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m_thompson
July 20th, 2014, 04:38 PM
My PDP-8/e is at the Rhode Island Computer Museum for repair. http://www.ricomputermuseum.org/Home/equipment/dec-pdp-8e

The processor is working OK now and includes a very nice 32k RAM board. The next step is to get the RX8E and an RX01 or RX02 working. The RX8E needed four ICs replaced, and it looks like it is working now. I have had little success running the RX8E diagnostics, so I wrote some simple ones to help with the debugging and repairs.

My idea was to get an RX01 working first to prove that the RX8E is OK, and then try to get an RX02 working. I have RX01 OS/8 images. I though that making real RX01 diskettes from the images might be more successful on an RX01 drive.

We have lots of RX01 and RX02 drives in the Museum's warehouse, but most of them look like they have a variety of problems. I was a little surprised to see that most of the drives labeled RX01 actually have RX02 controller boards inside.

Does anyone have a working RX01 or RX02 on a PDP-8/e that could try the DIRXA-C, DIRXA-D, or IRXAE diagnostics to see if they actually work?

vrs42
July 20th, 2014, 11:33 PM
My idea was to get an RX01 working first to prove that the RX8E is OK, and then try to get an RX02 working. I have RX01 OS/8 images. I though that making real RX01 diskettes from the images might be more successful on an RX01 drive.

I've never gotten anywhere trying to use my RX02 as an RX02. That seems to require the right drivers, etc.


We have lots of RX01 and RX02 drives in the Museum's warehouse, but most of them look like they have a variety of problems. I was a little surprised to see that most of the drives labeled RX01 actually have RX02 controller boards inside.

What I've always done is jumpered my RX02 to act like an RX01 and then just used it as an RX01. (I'm basically incredibly lazy about hardware debugging.)


Does anyone have a working RX01 or RX02 on a PDP-8/e that could try the DIRXA-C, DIRXA-D, or IRXAE diagnostics to see if they actually work?

My drive boots my 8/E just fine, so I'll try to find some time to insert a scratch floppy or two and see if I can get the diagnostics to do something.

Vince

Lou - N2MIY
July 21st, 2014, 04:12 PM
I can personally vouch that DIRXA-D works. However, I have only ever found the listing for -C. I would like to have a copy of the -D listing, if one exists.

To use an RX02 as an RX02 under OS/8, you must have the RX28 handler. This is a two page handler, and so you must have at least 12kW of core.

I have seen that most folks do use their RX02 drives as RX01 on their RX8E controllers. In my case, I do this because I can read/write RX01 floppies on an 8" drive I have connected to a PC. The only time I would use the RX02 as an RX02 is when using it on a decmate or if I want to read RX02 decmate floppes on the 8/e or 8/a for some reason.

Honestly, when I have made various repairs on my RX02 drives, I used the pdp-11 and XXDP maindecs to diagnose them.

Sorry to hear that your museum has so many broken drives. I'm afraid that museums often end up with piles of broken gear that will get no love.

Lou

vrs42
July 21st, 2014, 04:47 PM
I can personally vouch that DIRXA-D works. However, I have only ever found the listing for -C. I would like to have a copy of the -D listing, if one exists.

There is a write-up for DIRXA-D at http://www.pdp8online.com/pdp8cgi/query_docs/view.pl?id=1024
I'm in the process of creating a monster archive of MAINDEC files and docs, and that's where the SVN log says I got mine.


To use an RX02 as an RX02 under OS/8, you must have the RX28 handler. This is a two page handler, and so you must have at least 12kW of core.

I have seen that most folks do use their RX02 drives as RX01 on their RX8E controllers. In my case, I do this because I can read/write RX01 floppies on an 8" drive I have connected to a PC. The only time I would use the RX02 as an RX02 is when using it on a decmate or if I want to read RX02 decmate floppes on the 8/e or 8/a for some reason.

Yeah, I've got a bunch of old RX01 boot floppies, and they just don't seem to know what to do with an RX02.
As yet, I don't have a pile of RX02 boot floppies, so I just leave the drive pretending to be an RX01.

Vince

m_thompson
July 21st, 2014, 05:36 PM
Lou, can you tell me what parameters an SR settings you used with DIRXA-D?
Was that with an RX01 or RX02 drive?

Lou - N2MIY
July 21st, 2014, 06:20 PM
Vince,

You probably know this already, but bootable OS/8 RX01 media can't be booted on an RX02 in RX02 mode. It will work in RX01 mode though.

Thanks for the tip on the rev d listing. I will snag it now!

Lou

vrs42
July 21st, 2014, 07:04 PM
Vince,
You probably know this already, but bootable OS/8 RX01 media can't be booted on an RX02 in RX02 mode. It will work in RX01 mode though.


I didn't know it was impossible. I'd assumed I'd have to use the RX02 driver and make an RX01 with it as the boot device, or some such. I had always been too lazy to fuss around with BUILD and such to try it. Doesn't Charles Lasner brag about some floppy that boots on any model of PDP-8 with a drive? I guess that's not OS/8, though.

What I'm looking for now is some kind of machine readable key to the MAINDEC part numbers. It's looking like I'll have to type in the info for hundreds of diagnostics, which sounds like a pain.

Vince

Al Kossow
July 21st, 2014, 07:12 PM
Doesn't Charles Lasner brag about some floppy that boots on any model of PDP-8 with a drive?

yup, the OS only he has, and all others are, in his opinion, inferior to it.

Lou - N2MIY
July 22nd, 2014, 06:43 PM
Ok, I'm going to stir the pot a little...

I, like most others have only had P?S/8 dangled in front of them like a carrot all these years, reading about its virtues on alt.sys.pdp8. Does anyone here actually have or has anyone here actually seen P?S/8 run on real hardware? From previous correspondence on alt.sys.pdp8, I know there is no RL8A handler, nor TA8E handler, but I could run it off RX01 or decmate (I, II, or III).

The P?S itself is a mystery shrouded in an enigma with only small bits on the internet revealing much.

Lou

Uniballer
July 23rd, 2014, 12:52 AM
I believe I saw P?S running on a 4KW straight 8 with TU55's at Syracuse U. around 1981. I think it was Mark Hyde (but maybe Pat Gleason) who had a copy. Mark mentioned Charlie Lasner's name to me at least once. I never met him, but I did email with Charlie once in perhaps 1992 or '93.

This link might be of interest: http://web.archive.org/web/20091018013721/http://www.idkcomp.com/p?s.html

pbirkel@gmail.com
July 23rd, 2014, 01:02 AM
I believe I saw P?S running on a 4KW straight 8 with TU55's at Syracuse U. around 1981. I think it was Mark Hyde (but maybe Pat Gleason) who had a copy (and he mentioned Charlie Lasner's name to me at least once). I never met him, but I did email with Charlie once in perhaps 1992 or '93.

So, being a low-brow, please explain what a "P?S" is. I gather we're not talking about PS/8 -- the predecessor to OS/8 ....

Uniballer
July 23rd, 2014, 01:10 AM
Sorry, I didn't finish editing my last post before your reply. AFAIK, P?S is the PDP-8 operating system developed by the so-called Poly Question Society at Brooklyn Polytechnic Institute. See prior post for wayback machine link.

pbirkel@gmail.com
July 23rd, 2014, 01:15 AM
Sorry, I didn't finish editing my last post before your reply. AFAIK, P?S is the PDP-8 operating system developed by the so-called Poly Question Society at Brooklyn Polytechnic Institute. See prior post for wayback machine link.

Bulb lights, thank you. Never heard of it. Interesting acronym. Interesting society-name, too. What's so special about it?

Uniballer
July 23rd, 2014, 01:29 AM
Bulb lights, thank you. Never heard of it. Interesting acronym. Interesting society-name, too. What's so special about it?

I have no idea. I was never a member. I never even owned a PDP-8 that would have benefited from running P?S/8. I only heard a little about this stuff third hand from Mark Hyde and Pat Gleason (both of whom owned their own straight 8's when I was at S.U.).

Lou - N2MIY
July 23rd, 2014, 03:49 AM
From all that I've read that Charles wrote on alt.sys.pdp8 over the years, two important features stuck out:

1. device handlers are not limited to fit in two pages (allowing for much more sophisticated error handling) (and there's none of this business about needing at least 12kW of core to use two page handlers.)
2. over the years, it has been maintained in such a manner that it runs on more than the usual "family-of-eight" machines. That would be for example that a bootable RX02 would run on my 8/e and my decmate II (where right now, the decmate II needs OS78 V4 or OS/278 to properly support the hardware.)

Lou

pbirkel@gmail.com
July 24th, 2014, 12:02 AM
From all that I've read that Charles wrote on alt.sys.pdp8 over the years, two important features stuck out:

1. device handlers are not limited to fit in two pages (allowing for much more sophisticated error handling) (and there's none of this business about needing at least 12kW of core to use two page handlers.)
2. over the years, it has been maintained in such a manner that it runs on more than the usual "family-of-eight" machines. That would be for example that a bootable RX02 would run on my 8/e and my decmate II (where right now, the decmate II needs OS78 V4 or OS/278 to properly support the hardware.)

Lou

I'm up to three bulbs lit now :->. Thank you. Sounds nice. Why is it a bit like snark hunting?

(BTW, where's good place to find OS78 V4 and OS/278 images?)

Lou - N2MIY
July 24th, 2014, 03:52 AM
OS/78 V4 for the decmate I is here: http://www.pdp8online.com/images/images/os8/DECmate_I.shtml

David built this for a fellow in NH who had a decmate I. I bought that guy's decmate I some years ago. At any rate, it works perfectly. The diagnostic disk in this directory came with a broken (now fixed of course) decmate craigslist find of mine from a few years ago.

OS/278 for Decmate II and III is here: ftp://sunsite.unc.edu/pub/academic/computer-science/history/pdp-8/os8

P?S/8 however remains elusive......

Lou

pbirkel@gmail.com
July 24th, 2014, 11:46 PM
OS/78 V4 for the decmate I is here: http://www.pdp8online.com/images/images/os8/DECmate_I.shtml

David built this for a fellow in NH who had a decmate I. I bought that guy's decmate I some years ago. At any rate, it works perfectly. The diagnostic disk in this directory came with a broken (now fixed of course) decmate craigslist find of mine from a few years ago.

OS/278 for Decmate II and III is here: ftp://sunsite.unc.edu/pub/academic/computer-science/history/pdp-8/os8

P?S/8 however remains elusive......

Lou

Excellent information Lou. Thanks :->.

m_thompson
July 26th, 2014, 05:45 PM
I went back to a more structured approach to testing the RX8E diskette controller board. I used the small diags that I wrote to exercise parts of the RX8E circuitry, looked at the signals with a 'scope to make sure that everything was OK, and then used a highlighter to mark the signals and gates that have been tested on the RX8E schematic. I have about 85% test coverage now.

I need to figure out how to get data into and out of the Transfer Register in Maintenance Mode to get the test coverage to about 95%. It looks like I can execute an LCD IOT with the Maintenance Bit on, then execute an LCD IOT with all bits on, and the Transfer register will contain all of the bits. Executing an XDR IOT will move the contents of the Transfer Register back to the AC. Variations on this theme will all me to test all of the bits in the Transfer Register except for bit 4.

I will need partially working RX01 or RX02 diskette drives to test the remaining 5% of the circuitry because it needs signals from and to the RX01 to exercise the circuitry on the RX8E.

Once I get to 100% test coverage on the RX8E I will go back to debugging an RX01. Many people said that the RX02 diskettes will not pass all of the RX8E diags and will not boot OS/8 in double density with a 32 instruction or less bootloader that will fit in a MI8E board, so I will stick with and RX01 drive.

Lou - N2MIY
July 27th, 2014, 06:08 AM
Many people said that the RX02 ..... will not boot OS/8 in double density with a 32 instruction or less bootloader that will fit in a MI8E board, so I will stick with and RX01 drive.


That part is correct. The RX02 bootstrap will not fit in an MI8E. I have my MI8E set up for RX01. Remember though, you can still use the RX02 drive, it must be jumpered to behave as an RX01. That is the setup I have on my 8/e.

Lou

m_thompson
July 27th, 2014, 05:10 PM
I did some more debugging today. Yesterday the processor died. If it executed an Operate instruction the PC got loaded with a strange address. Replacing the M8310 Major Register Control board fixed it.

19613
In this image you can see the RX DATA and the D3 CLK BUFF L signals when the RX8E and the RX02 are talking.
The Status word says that the drive is not ready, so I have some RX02 debugging to do.

Lou - N2MIY
July 27th, 2014, 07:04 PM
Are you going to fix the broken M8310?

Lou

m_thompson
July 28th, 2014, 05:31 AM
Lou,

When I started this PDP-8/e project the M8650 had just one failed SN7474 IC, so that was an easy fix. Both 8k core stacks had different problems, so they were replaced with a 32k RAM board from Vincent. In the last two months the M8300, M8310, and M8330 all failed and were replaced with spares. After I get the RX8E/RX01, TD8E/TU56, and MI8E working I will make two extension ribbon cables so I can put the processor and core boards on an extender and repair them. If I get all of that working I might get brave and start looking for an RK8E. Details on this project are here: http://www.ricomputermuseum.org/Home/equipment/dec-pdp-8e/pdp-8e-restoration-log

I have a long term project to connect an Actel SmartFusion FPGA to the Omnibus so it can emulate peripherals that I don't have. The idea is to put time sensitive logic like address decoding, skip, data break, and interrupt in the FPGA and do all of the non-time sensitive emulation with Linux device drivers and Linux applications running on the ARM in the FPGA. There is enough RAM in the SmartFusion so I could copy a disk/tape image from flash memory to RAM, emulate disk/tape from the RAM image, and copy the RAM image back to flash when the processor halts. Having the flash images of the disk/tape in Simh format would be convenient. The SmartFusion has analog I/O so I could emulate an A/D converter. Another enthusiast suggested making a Web peripheral where you would write a URL to the device, the SmartFusion would fetch the file from a Web server, and then the 8e application could read the file from the Web peripheral. Kind of like NAS for the 8e. I did a proof of concept project like this for the PDP-8/L. Info is here: http://www.ricomputermuseum.org/Home/equipment/pdp-8-l/making-a-posibus-periperal-emulator

Lou - N2MIY
July 28th, 2014, 04:51 PM
Sounds like a great project. You are fortunate to have boards to pull and swap. I have gate chased problems in my central processor (and repaired them) three times over the years. (No swap boards here, but boatloads of TTL, scope, logic analyzer, prints, the three volume service manual set.) I hope the swap boards get repaired - these boards are not cheap or easy to come by.

Lou

bobaboba
July 29th, 2014, 01:00 AM
I've found that bringing an old machine up after a long time without power does end up with a few IC failures. I've had to replace several in the one I'm working on at present. Mine have generally worked to begin with but died after a few operating hours. I guess that moisture has found it's way in over the years and then the heat when powered up leads to an early failure.

As you say though - it's important to fix the boards where possible, they are now quite scarce on the secondhand market. I have only a small stock of TTL and it can be a longish job looking for a spare then finding that you worked it out wrong. I have an extended memory controller playing up just now which can set any field from power-up but not change it after that. Some memory stacks which are a bit flaky too - I find them near-impossible to work on with marginal fails and difficult access.

m_thompson
July 29th, 2014, 05:45 AM
The team at the Rhode Island Computer Museum revived a PDP-9, PDP-8/S, 8/L, 8/I, and now the 8/e. The common procedure is to replace the AC capacitors in the ferroresonant power supplies first because they always fail. Then connect just the power supply to AC through a Variac and very slowly increase the voltage while measuring the voltage on the caps, looking for bulging caps, and measuring the temperature of the caps. We also look for electrolytic caps on the boards, and reform them. Once the power supply works OK we can power up the system at full voltage.

The 8/S system required cleaning, front panel bulbs, and power supply caps, but not much else.

The 8/L required repairs to 28 Flip-Chips and had the symptoms that bobaboba described. It would run for a while and then die. We replaced lots of SN7474 ICs and a few other TTL parts.

The 8/I was stored in a poor environment for a very long time and required repairs to 51 Flip-Chips. The ICs that failed were mostly SN7474 and SN7440. The most difficult issue to find was a broken Wire-Wrap wire on the backplane.

Warren made a Flip-Chip tester that was a huge help with testing and repairing the 8/I, 8/L, and the spare Flip-Chips.

The PDP-9 is transistor only like the 8/S. It is microcoded and has lots of delay lines that must be adjusted by Wire-Wrap jumpers on the backplane to control timing. It is much more complicated than a PDP-8, but does have some built-in diagnostic capability. Using two 'scopes and a logic analyzer at the same time was the only way to debug it. It has been a significant challenge to get running and keep running, and spare boards are rare and expensive.

The PDP-8/e is actually a lot easier to debug than the 8/I or 8/L. With everything on one board we can just put the suspect board on an extender and start debugging. I have an HP logic comparator that I will start using on this system. You put a known good IC in the Logic Comparator, clip the probe over the suspect IC, and run the machine. Any difference in the behavior between the known good IC and the one on the board will show up in the LEDs. I need to make ribbon cables for the cross-over connectors so I can debug the CPU and core boards. As long as the current set of CPU boards stays working I will work on the diskette and tape subsystems. If the CPU dies again I will fix all of the CPU boards so I have spares again.

DaveH
August 2nd, 2014, 01:48 PM
Sounds like a great project. You are fortunate to have boards to pull and swap. I have gate chased problems in my central processor (and repaired them) three times over the years. (No swap boards here, but boatloads of TTL, scope, logic analyzer, prints, the three volume service manual set.) I hope the swap boards get repaired - these boards are not cheap or easy to come by.

Lou

Personally I find repairing boards stimulating and very satisfying and would add lots of coffee to the "tools" needed :) so far the only ones that have defeated my are actual failed core stacks.
I do have quite a few ;)
19700

Dave

m_thompson
August 3rd, 2014, 09:32 AM
Personally I find repairing boards stimulating and very satisfying and would add lots of coffee to the "tools" needed :) so far the only ones that have defeated my are actual failed core stacks.
I do have quite a few ;)Dave

I agree that it is satisfying to track down a broken IC and fix a board. The RICM has a pile of repaired and tested Flip-Chips that looks like yours. We put tags on them indicating the failure and what was replaced to fix it. Warren Stearns made a Flip-Chip tester that connects to the parallel port on a PC and uses SPI expander chips to control and read the signals. It was really helpful getting the 8/I and 8/L running.

Warren's board tester doesn't do negative logic, so on a few occasions we jumpered a few Flip-Chips together to test Flip-Chips from the PDP-9. That would also work for a Classic PDP-8, TC01, TC02, TC58, TC59, etc. We have a big stack of PDP-9 Flip-Chips that need to be repaired.

I have swapped email with several people who have repaired core stacks from early DEC equipment. Usually the wires in the core stack were broken and soldered during manufacturing. The solder joints come apart after 40 years and need to be resoldered. The later core stacks used in the PDP-11s are probably too dense to repair.

m_thompson
August 3rd, 2014, 11:27 AM
I did some more RX8E debugging yesterday. I debugged the Transfer Register test that I wrote. That exercised and validated more logic.

I tried the RX01 again. Pressing the CLEAR key did not reset the RX01. I replaced the digital board with one from a desktop RX01 and now it almost always resets in the CLEAR key. It is nice to see the heads move and the head load solenoid activate. It looks like the processor is not always activating the INIT signal on the Omnibus when you press the CLEAR key or execute a CAF instruction. Power cycling the whole system fixes that issue. I will debug that later.

Reading the RX01 Status and Error Registers exercised the remaining RX8E logic, so I think that the RX8E is ready to go. I see the Drive Ready and INIT Done bits in the Status Register, and a error code of 0170 Data AM not found in allotted time, or 0200 CRC error on reading the sector from the disk.

I started looking at the signals on the analog board. The disk Index pulse for DK0 is every 170 ms, for DK1 it varies a lot. The drive door latch is not working well so the hub is slipping.

I will write a sector buffer test this week.

Next Saturday I will replace the right diskette drive with a NOS spare. I will also look at the signal from the head and trace it back through the digital board. I should check the diskettes on a PDP-11 because they might have been damaged by all of the debugging and experimenting.

m_thompson
August 10th, 2014, 06:23 AM
The intermittent with the CLEAR key turned out to be in socket E7 for one of the microcode ROMs on the M7726 logic board in the RX01. Wiggling the ROM fixed it for now. I need to take all of the ROMs out and treat the sockets with DeoxIt for a permanent fix. After fixing the microcode problem the DIRXA controller and the controller-interface diags passed and printed a "C" after every pass. I tried the complete diskette diagnostics and saw the same 0170 Data AM not found in allotted time, or 0200 CRC error on reading the sector errors.

Earlier this week Warren and I came up with a plan to look at the differential signals from the diskette head, and work through the Op-Amps to the One-Shots. I really couldn't see any more than a few millivolts from the diskette head, so I verified that the head select logic was all OK. I swapped the diskette in case it was damaged by earlier experiments, and noticed that there was a radial wear line on the diskette where the head touched. I poked a flashlight inside the diskette drive and was not really surprised to see that the diskette spindle was not turning.

Last week, I had disassembled the right drive to remove a big red piece of plastic and a cardboard puzzle piece. At the same time I cleaned the head, the index and track 0 sensors, and put the drive belt back on the pulleys. It is not unusual to have the belt stick to the pulleys and fall off if the drive hasn't been used for a very long time. I stopped debugging then, and forgot to do the same procedure this week for the left drive. I put the belt for the left drive back on the pulleys and now I could see the head stepping out the tracks when the diag was running.

It still failed, but with mostly with a 0200 CRC error on reading the sector errors. I tried several different diskettes and got different results. I ran a cleaning diskette in the drives, and didn't see any improvement. I dug through the warehouse looking for NOS single-density 8" diskettes. I found lots of double-density and some hard-sectored diskettes and just a few single-density. One of the NOS diskettes works perfectly and the left drive passes all diagnostics. It prints a "D" at the end of every pass.

I need to find more good single-density 8" diskettes or get one of the S-100 systems that will format diskettes working. Next week I will try David Gesswein's restrx01 program to see if I can copy an image of a diagnostics diskette to a real diskette. If that works, the diskette should boot to OS/8.

Lou - N2MIY
August 10th, 2014, 04:45 PM
Don't forget to check the little felt dot on the underside of the head load solenoid arm. Sometimes it's gone, sometimes it's really smashed down.

Any person intending to do much with an RX01 should set up a PC with an 8" floppy drive. Then with PUTR and IMGDSK you can format RX01 media, make complete images of your disks, and even work with the files of RT-11 or OS/8 formatted disks.

I've written about it here before, but I take dime-a-dozen double sided floppies, punch the index holes through the jacket in the right place, and then have RX01 flippy disks (one RX01 on each side). Format them on the PC and you're good to go.

If you're really serious about 8" floppies, you'll also get an analog alignment disk. All of its usefulness has been explained here before also.

Lou

m_thompson
August 11th, 2014, 09:35 AM
I just sent an email to John Wilson asking about an FDADAP so I could format RX01 floppies and copy files onto them.

Lou - N2MIY
August 11th, 2014, 04:48 PM
It's trivially simple. You can wirewrap it yourself. See here: http://www.classiccmp.org/dunfield/img/index.htm and click on the link entitled "connecting 8" and external floppy drives" .

Here is a picture of my rig: http://www.vintage-computer.com/vcforum/album.php?albumid=2&attachmentid=2381

Lou

m_thompson
August 11th, 2014, 04:56 PM
Lou,

I think that the trick is finding a PC that has a floppy controller that is versatile enough to be used with a variety of diskettes. I will go through my collection of PCs and see what they have for controller ICs.

m_thompson
August 11th, 2014, 05:03 PM
I used DeoxIt to clean and treat the microcode sockets in the RX01. Hopefully the RX01 intermittent is gone for good.

We booted OS/8 through the serial port using Kyle Owen's serial server, and used the OS/8 RXREAD program to test some 8" floppies. Out of the stack of diskettes from a variety of vendors we found three that worked OK. I need to get a PC setup with an 8" floppy so I can format and image 8" diskettes.

I used David Gesswein's dump/restore programs to copy an image of an OS/8 diskette to a real RX01 diskette. After trying three different RX8E bootloaders, the one in the OS/8 manual booted OS/8 from the diskette that we just made. I even ran BASIC from the diskette, so that probably means that the processor is working OK.

SYS VOLUME-- 1
SYS:=RX8E
OS/8 SYSTEM VERSION 3Q

BUILD .SV 33 HELP .SV 8 BASIC .UF 4
ABSLDR.SV 5 PAL8 .SV 19 BCOMP .SV 17
BITMAP.SV 5 PIP .SV 11 BLOAD .SV 8
BOOT .SV 5 PT8E .BN 1 BRTS .SV 15
CCL .SV 18 RESORC.SV 10 EABRTS.BN 24
CREF .SV 13 RXCOPY.SV 6 RESEQ .BA 6
DIRECT.SV 7 SABR .SV 24 ECHO .SV 2
EDIT .SV 10 TECO .SV 22 RKLFMT.SV 9
EPIC .SV 14 BASIC .AF 4 SET .SV 14
FBOOT .SV 2 BASIC .FF 4 BATCH .SV 10
FOTP .SV 8 BASIC .SF 4 FUTIL .SV 26
HELP .HL 55 BASIC .SV 9 IDS .SV 5

36 FILES IN 437 BLOCKS - 1 FREE BLOCKS

The right diskette drive is not working well, so we still need to fix that.

Lou - N2MIY
August 11th, 2014, 05:24 PM
Most excellent. Congratulations!

You will find very soon that you'll want to configure your MI8E for the RX01 bootstrap. Fat fingering it in gets old fast.

For someone else here I placed my MI8E on a flatbed scanner and took a picture. All one needs to do is follow the picture and put all the diodes and jumpers in the right places. I worked it all out by hand myself when I did it, but there is no sense in anyone going through the same pain.

Lou

pbirkel@gmail.com
August 12th, 2014, 12:41 AM
I used DeoxIt to clean and treat the microcode sockets in the RX01.

Which one, and how? I've seen general mention of DeoxIt in various contexts, but their product line seems to have a plethora of variants.

I'd like to learn more about your/others experiences & uses, please :->. Thanks! [Maybe this topic deserves a new thread?]

-----
paul

m_thompson
August 12th, 2014, 05:32 AM
Which one, and how? I've seen general mention of DeoxIt in various contexts, but their product line seems to have a plethora of variants.

I use both DeoxIT® D-Series (D5S-6) and DeoxIT® Gold G-Series (G5S-6). I use the D-Series for cleaning and lubricating tin contacts, and the G-Series for gold contacts.

m_thompson
August 12th, 2014, 05:40 AM
You will find very soon that you'll want to configure your MI8E for the RX01 bootstrap. Fat fingering it in gets old fast.

I have been RIM loading the RX01 bootstrap, but getting the MI8E working is next on my list. The MI8E prints don't include the RX01 bootstrap so I would be interested in having a copy of your picture.

I found many different RX01-RX02 bootstraps, but only the one in the OS/8 manual worked.

Lou - N2MIY
August 12th, 2014, 04:36 PM
Mike,

Send me a PM with a proper e-mail address so I can mail you the photo (and anyone else interested.) It's too big for the photo album here on the forums, and the high resolution is important. Perhaps you can post it for everyone somehow with your project blog.

Lou

pbirkel@gmail.com
August 13th, 2014, 01:12 AM
I use both DeoxIT® D-Series (D5S-6) and DeoxIT® Gold G-Series (G5S-6). I use the D-Series for cleaning and lubricating tin contacts, and the G-Series for gold contacts.

Thx! Anyone ever use the bottle-with-brush instead? Then a standard compressed-air can for clean-up? Appears to be more cost-effective, if less convenient.

m_thompson
August 16th, 2014, 04:55 PM
We fixed the 854 power controller. Now the AC power for all of the peripherals is controlled by the key on the processor cabinet.

The 8/e would not boot OS/8 from the RX01 floppy today. It worked OK after we reseated the microcode ROMs in the RX01 diskette drive. To make it more reliable we removed the microcode ROMs, cleaned the tim plated leads, treated them with DeoxIt, and reinstalled them. The RX01 works OK now, and hopefully it stay that way.

The right diskette drive doesn't work correctly. While running diagnostics we compared the INDEX, TRACK 0, and RAW DATA signals from the two drives. As far as I can see they both look the same. The controller was reporting "A Preamble Could Not Be Found" errors. Next week we can swap the two drives to see if the problem is in the analog board or the diskette drive.

m_thompson
October 13th, 2014, 05:22 PM
Only the left diskette drive on the PDP-8/e works so we swapped the left & right diskette drives. If the reading problem is in the drive the problem will follow the drive. If the problem is in the analog board in the RX01 the problem would not follow the drive. The problem followed the drive, so we know the analog board is OK.

We found a diskette drive in the warehouse that had "RX01 ONLY" silk screened on the side, so we tried that one. The replacement drive had a resistor in the read/write head connector and one on another signal connector. The replacement drive didn't work, even after removing the resistor on the head connector.

Now that we know the problem is in the drive, we can compare the signals between the working and broken drive to see if I can isolate the problem and possibly fix the diskette drive.

m_thompson
October 25th, 2014, 05:37 PM
We replaced the left diskette drive in PDP-8/e again today, and actually found another one that works! This one looks like a slightly newer model because it has a resistor in the data head connector. The resistor is only used in RX01 subsystems, so the diskette must also work in the newer RX02 subsystem.

So now both diskette drives are working.

Time to fix the MI8E bootstrap board so the 8/e will boot from diskette with the push of a button.

m_thompson
November 2nd, 2014, 08:37 AM
I bought an MI8E bootstrap board from William Donzelli a few months ago. This board contains a 12x34 diode array that is really a ROM containing bootstrap code. The board is manufactured with all diodes installed (0 bits) and diodes are cut out to represent 1 bits. When you toggle the SW switch on the front panel the MI8E board emulates someone flipping the switches on the front panel to toggle in and run a bootstrap loader. The one that I bought contains the RX8E diskette bootstrap.
I installed the MI8E, toggled the SW switch, and was really surprised when OS/8 booted from the floppy. A 40 year old board worked without any repairs!

Now that both floppy disk drives are working it was time to attempt recovering my wife's Masters thesis from 8" floppies. She did all of the thesis documents on a DEC WT-78 word processing system quite a while ago. DEC used two recording formats for 8" floppies on the PDP-8. One was 12-bit based and one was 8-bit based, and both were IBM SSSD format. The PDP-8/e can use either version. The OS/8 installation that I am using defaults to 12-bit mode, but the console command "SET HANDLER FLOP=BYTE" will change the floppy disk device handler to 8-bit mode. Doing a DIR on the WT-78 floppy yielded a "bad directory", which was what I expected with a decades old floppy. Further investigation showed that DEC made a program "WPFLOP" to read/write Word Processing floppies. I used the console command "R WFLOP" to run the program, and "RXB1:1" and hit the Escape key to type file #1 on the console. Word Processing file #1 conveniently was the file directory listing. Using WPFLOP I have recovered 2/3 of the Masters thesis files and have converted it to an MS Word file. I will convert the remaining files tomorrow.

jackrubin
November 2nd, 2014, 09:24 AM
Very nice - I think you've more than earned an "easy one"! Even better that you get points with your wife for helping her out!

What is the Y suffix on your board? The printset I have from bitsavers lists variants from YA through YM but nothing for the RX8E.

I am currently using a reconfigured blank board to boot SerialDisk and plan to convert a YE (Typset RIM) to RX8E using information from Lou Ernst. It would be interesting to compare his version with yours.

Jack

m_thompson
November 2nd, 2014, 12:52 PM
My MI8E is the same as Lou's. He sent me pictures of his, the source code, and the diode cut list.

jackrubin
November 2nd, 2014, 06:17 PM
Sorry for the confusion - from your description, it sounded as if the card was already pre-configured for the RX boot when you got it form Will. I've got a few of the boards here, some OK, some not so OK.

Question for anyone who has played with one of these boards - have you been able to locate the ENABLE flipflop mentioned in the trouble shooting section on page 4-7 of the manual (actually Chapter 4 of Volume 2 of the PDP-8/E Maintenance Manual)? I can't find it on the print and at first figured it was a typo, that the manual was referring to the DATA f/f since it has two enable lines coming out of it but in the next paragraph the DATA f/f is referenced.

Jack

m_thompson
November 3rd, 2014, 05:16 AM
Jack, There are no signs of any soldering on the MI8E that I have, either in the diodes or the jumpers, and there are magic-marker dots next to the jumpers that were removed to to set the addresses. I can't tell if this was a generic MI8E that someone configured for the RX01, or if it was done at the factory. I will take some pictures of it and post them on the RICM WWW page.

m_thompson
November 9th, 2014, 08:27 AM
We used David Gesswein's dumprest tools to make new diskettes from images. So far we have bootable OS/8 with diagnostics, OS/8 with Fortran-IV, and COS-310. COS-310 was targeted towards business use, but we haven't found a copy of the DIBOL language to run in it. We are also looking for a copy of the WPS word processing software to run under OS/8. None of the diskettes have support for the DECtape, so we will need to learn how to reconfigure the OS handlers.

The MI8E bootstrap board is very nice. Just toggle the SW switch and it boots from diskette.

m_thompson
November 16th, 2014, 06:57 AM
21506
I made a diskette of the WPS word processing software for the PDP-8/e. It booted and ran just fine, and I was able to look at the the files on the diskettes that contained my Wife's master's thesis. I was surprised to see that the contents of the MQ register display on the front panel of the 8/e was cascading lights while it was running. Someone at DEC had too much time on their hands! We have an LQP-02 printer, so I might see if I can get that connected and working with WPS.

WPS normally ran on a dedicated WT78 that was a PDP-8 microprocessor inside of a VT-52 terminal. This was very cool stuff 30 years ago.

Lou - N2MIY
November 16th, 2014, 07:11 AM
Mike,

This is great. I always wanted to do this myself. Can you provide some detail as to where you found the disk image? Not all WPS-8 systems were run on VT78 or decmates. There were large systems called WS200 that used an 8/a, supported multiple terminals, and stored files on RL02. I have a pocket service guide for those systems which I need to scan and get to David G. someday.

I have bootable WPS RX02 for my decmates, but never saw a bootable RX01 with WPS. If it's not too much trouble, can you e-mail me or post a link to an imagedisk image of this floppy?

Thanks,
Lou

m_thompson
November 16th, 2014, 01:22 PM
Lou,

I got the ws78_v3.4_wps_system_disk.rx01 image from Dave's WWW page at ws78_v3.4_wps_system_disk.rx01.

I don't have a clock board in my 8/e, so the elapsed time and the date/time on WS78 don't change.

I need to get a VT-52 and LQP-02 connected to the 8/e so my wife can have flashbacks to working on a new WP-78.

Seeing your WS200 service guide would be interesting.

m_thompson
November 21st, 2014, 10:30 AM
Where can I get some RX01 SSSD 8" floppies to go with this system?
Used are OK.

tradde
November 21st, 2014, 10:48 AM
Where can I get some RX01 SSSD 8" floppies to go with this system?
Used are OK.
I might have some. I have two hard cases (one plastic, one cardboard) full. But they may not be SSSD.
I'd have to look. You are likely to find someone closer that may have them too. I'll take a look at what
mine are.

Marty
November 21st, 2014, 11:31 AM
Hi All;
For those of Us, Like me not in the know..
Are these Hard Sector OR Soft Sector, ecxept for needing to be Formatted, would any 8" work as long as it was the same type, Hard vs Soft Sector ??

THANK YOU Marty

MattisLind
November 21st, 2014, 12:00 PM
Hi All;
For those of Us, Like me not in the know..
Are these Hard Sector OR Soft Sector, ecxept for needing to be Formatted, would any 8" work as long as it was the same type, Hard vs Soft Sector ??

THANK YOU Marty
RX01 is soft sectored. This is hard sectored:

https://dl.dropboxusercontent.com/u/96935524/Datormusuem/Incoterm/Hard%20sector%20diskette%20for%20Incoterm.png

Used on the Incoterm SPD 10/20 (http://www.datormuseum.se/peripherals/terminals/incoterm-spd-20-20). They still need to formatted but the start of a sector is indicated by a hole in the diskette. I think that a hard sectored disk would work fine in a soft sector drive.

Marty
November 21st, 2014, 03:59 PM
Hi All;
MattisLind, "" I think that a hard sectored disk would work fine in a soft sector drive. "" NOT Usually.. Now my experience is with Shurgart 8" Drives, But, I would say NO !! I know the Difference, I have Hard Sector for my Altair 8800 and I have Soft Sector for when I am running with John's Z-80 and ZFDC Board.. A hard Sectored Diskette has tooo many holes for a soft Sectored system..
And the one You are showing has the Sector Holes in the Wrong place, from what I have.. So maybe RX01 has its sector hole different than mine..

21538 21539 21540

THANK YOU Marty

Lou - N2MIY
November 21st, 2014, 05:53 PM
Marty,

The hard sectored disks for your system look a lot like an RX01. The sector hole is in the usual place (near the hub), but there is one hole for each sector. Long long ago you might remember the 2 and change boxes of Memorex hard sectored floppies I sent you. The reason the third box was partially full was because way back, out of desparation, I opened the jacket on one of those floppies, took the media out of the jacket, and cut a ring of tape to block all but one sector hole. That basically turned the hard sectored disk back into a soft sectored disk. I did format it as a real dec RX01 in my DSD440. I still have that disk (but didn't use it much as I was luck enough to find a guy nearby with some soft sectored disks.

Lou

Marty
November 21st, 2014, 06:05 PM
Hi All;
Yes, Lou, I remember.. I guess that would be approach, "" and cut a ring of tape to block all but one sector hole. ""
And with my Pictures, I was trying to show the difference between the two..

THANK YOU Marty

MattisLind
November 22nd, 2014, 12:24 AM
Hi All;
MattisLind, "" I think that a hard sectored disk would work fine in a soft sector drive. "" NOT Usually.. Now my experience is with Shurgart 8" Drives, But, I would say NO !! I know the Difference, I have Hard Sector for my Altair 8800 and I have Soft Sector for when I am running with John's Z-80 and ZFDC Board.. A hard Sectored Diskette has tooo many holes for a soft Sectored system..
And the one You are showing has the Sector Holes in the Wrong place, from what I have.. So maybe RX01 has its sector hole different than mine..

21538 21539 21540

THANK YOU Marty

You are right, Marty. The disk in my picture is clearly NOT compatible since the sector / index hole is at the rim of the disk rather than close to the hub. I was confused...

I just wonder how many variants of 8 inch disks there were once upon a time?

psandy
November 23rd, 2014, 02:41 AM
You are right, Marty. The disk in my picture is clearly NOT compatible since the sector / index hole is at the rim of the disk rather than close to the hub. I was confused...

I just wonder how many variants of 8 inch disks there were once upon a time?

Memorex had a hard sectored physical design and Shugart had a soft sectored. More importantly the two disk types had different sector hole locations and also different write protect methods. The Memorex had a "cut-off" corner that you completed with a glue on tag to write protect the disk. You can see the cut out in the previous photo. The Shugart has a foil tab that was folded around the floppy case quite near the read/write hole.

Mmemorex was used by Vydec wordprocessors, Incoterm SPD 10/20s (I worked on both). Most other systes used the Shugart style, including all S100 systems I saw

m_thompson
November 30th, 2014, 07:16 AM
https://dl.dropboxusercontent.com/u/96935524/Datormusuem/Incoterm/Hard%20sector%20diskette%20for%20Incoterm.png

Mattis, the RICM received two boxes of those strange diskettes yesterday. The box says that they are for Lexitron and Memorex systems. The RICM has a Lexitron system, so they might be useful.

m_thompson
September 24th, 2015, 05:31 AM
I put my 8/e back together this week, and the RX01 is misbehaving again. I wiggled the microcode ROMs in the RX01, and the heads now wiggle when the you press the Init switch on the 8/e. It still won't boot though. Maybe it is time to replace the cheap sockets on the RX01 digital board with more reliable screw-machine sockets.

DrCharles
September 26th, 2015, 07:58 PM
I got a clean RX01 from Vince, and bought a somewhat pricey RX8E which arrived today. I don't know if either one is actually working but at least I have a complete system, and an unopened box of 3M DSDD 8" floppies. Let the debugging commence...

My copy of OS/8 is from the diagpack2.rk05 image. It does have RX handlers but after loading RXNS.BH, the device showing in BUILD is RX02. Will this even work with an RX01 drive or do I need a different handler? I installed RXA0: and RXA1: but any attempt to read or write to those devices hangs OS/8. The heads can be heard to "clunk" several times when the power is turned on, but I don't hear anything afterwards. It's pretty noisy in here with the 8/A fans, two RL02's and a Teletype but I expect to be able to hear something if the drive is being accessed.

AIRXAE.DG is showing errors so I have to read the manual to know how to interpret them... or just start systematically testing the logic with toggle-in programs as already posted here...

Edit: the errors are control/interface, not even getting as far as reading/writing the drive.
(after about a 5 second pause, printing the heading ERR FAT FAST EAC GOOD PASS with 475 435 435 0 0 0 0).
DIP switches on the RX8E are now set to x75x which is apparently the default for the diagnostic (not x70x as the RX user manual says).

-Charles

m_thompson
September 27th, 2015, 07:26 AM
You will need SSSD or DSSD diskettes for the RX01. The RX01 will not be able to find the sectors on the DSDD diskettes that you have.

I wrote some simple diags to help debug the RX8E and the RX01. I can post them here if you like.

DrCharles
September 27th, 2015, 07:41 AM
My mistake... I mistyped, they are in fact SSSD. Got lost in the alphabet soup. SSDD ;)

Yes, please post the diagnostics. Thanks!

I'm going to start with the basics... simple loop to access the IOTs and scope them, and go from there. It's a bit annoying to have to do this considering what I paid for the RX8E :roll: but at least it's simple TTL and I'm sure I can find it. The schematic is only 3 pages. My last major debug was an RL8A and that is 10 pages.

DrCharles
September 27th, 2015, 09:42 AM
The new-to-me RX8E doesn't do anything... so far I have found that the IOT logic is working, but the 8640 (E11 pin 9 in/14 out) that buffers TP3 clock pulse from the Omnibus is apparently stuck high.

The waveform coming into the gate looks OK on pin 9, short positive-going pulses, but the inverting output is not moving low at all,and it takes over 30 ma to forcibly pull it low (there are only six standard TTL inputs driven by that line, so the spec is 9.6 ma max to pull to 0.8v or less).

To verify, I disconnected that output pin on the 8640 from everything else and it still requires 28 ma to pull down and there are no pulses even with no load.
When I manually toggle the buffered TP3 line with the 8/A executing continuous INIT commands, the drive heads "cluck" as they are moved to Track 0 each time I create a pulse.

Good thing I have a spare 8640... hope there's not too much more of this :P

DrCharles
September 27th, 2015, 10:27 AM
I changed the 8640 (and put a socket in, which I always do when replacing a chip) and now the controller is OK. The drives audibly initialize when I hit the INIT key on the programmer's panel, too, which it was not doing before. Forgot how noisy those things were (haven't used one since about 1983!) I can hear the re-init clunking from downstairs!

I'm running diagnostics but getting some errors in what looks like the middle tracks (47-52) of drive 0. This AIRXAE (under OS/8) diagnostic is not particularly user-friendly, but with help from the MAINDEC listing I'm getting somewhere. It gives cryptic abbreviations and number codes instead of the more useful text messages that the RL diagnostics give.

The TTY is printing something once in a while, will go check in a few while letting the drives run and get their oil warm ;) Hope it's mostly pass-complete messages, it sounds quite short.

Wonder if a good head cleaning is in order... haven't yet read enough of the manual to see if there may be a maintenance need, or a simple check, for head alignment or track 0 setting.

Edit: it has now run over 20 passes with no further errors, testing both drives. It prints PASS nnnnD. Apparently that is great news!
The MAINDEC listing says the "D" means RX8, RX01 and drive all tested OK (the initial pass with errors had a "-" meaning that an error occurred in either the interface, control or drive).
:happy2:

Best of all, they now work under OS/8... got BAD INPUT DIRECTORY at first, but then I remembered I had to ZERO the directory of a new disk before use. After that, RXA0: and RXA1: both have 487 free blocks and can be read/written from. Perfect! :D

BTW has anyone got a spare set of outer rails (the part that bolts to the rack)? I only have the inner slides (that bolt to the drive).

thanks
Charles

m_thompson
September 27th, 2015, 12:43 PM
The source, listing, and RIM files for the simple RX8E/RX01 tests are in the attached ZIP file.

DDS
September 27th, 2015, 02:19 PM
"BTW has anyone got a spare set of outer rails (the part that bolts to the rack)? I only have the inner slides (that bolt to the drive)."

That's a lot more common than you might think. When a system is being scrapped the tear out crew typically pulls the drive out on the slides, cuts all the cables, then lifts the drive out. Half the slide stays with the drive and the other half gets scrapped with the rack. I've had some success with buying that kind of stuff from Pinnacle Micro although things seem to go in and out of stock. I'm sure there are other sources on the web.

DrCharles
September 27th, 2015, 02:51 PM
Any idea where I can find the DEC part number (which Pinnacle expects)? I looked through the RX01 Engineering Drawings but don't see it... Or is there a generic slide set I can buy and drill holes if needed?