PDA

View Full Version : Owning and operating an S-100 bus computer



JNZ
September 25th, 2015, 03:49 PM
A few weeks ago I made a thread asking about the feasibility of owning and operating an S-100 bus computer. I learned about N8VEM, Zeta 2 SBC and alternative ECB cards, signed up for the N8VEM wiki, and discovered there's still a reasonably active homebrew community creating new ECB and S-100 bus cards.

And now, thanks to the great generosity of new_castle_j of this forum, I was able to obtain a homebrew S-100 bus computer with a few cards! He sent it to me for the cost of shipping, along with documentation, extra 8" disks, and an extra front panel project he had. He also very helpfully sent me a copy of the EEPROM from the Z80 board, as well as physical and digital copies of the machine's boot disk. I'm extreme grateful for this; thanks again!

https://i.imgur.com/ldxzqxYm.jpg (https://i.imgur.com/ldxzqxY.jpg)

(Cat for scale)

The machine is built up around an S1-MOD 12-slot fully terminated motherboard by Delta Products of Huntington Beach, CA. The manual actually has no copyright or publication date anywhere on it (one of its peculiarities), so I'm not sure exactly when the machine was assembled. Likely in the early to mid-80s, based on the boards I'll describe in a moment. It's contained in a hand-built oak case, which has one side for the board and the other for two 8" disk drives. The case itself is quite well built, having dado joints to recess the panels and a removable top to grant access to the S-100 cards.

https://i.imgur.com/7LT1d6Rm.jpg (https://i.imgur.com/7LT1d6R.jpg)

The linear PSU has, and in addition to the rectifier output that goes to the S-100 bus, a few Molex-style connectors that provide regulated power to the 8" drives and other peripherals. It appears to have an additional in-line fuse, and, disconcertingly, there's an unshielded screw terminal in which (fused) 110V AC is broken out to the drives. There's no back to the case, probably for airflow reasons...so little fingers or a curious cat could, in theory, touch live AC.

https://i.imgur.com/LyjkCWHm.jpg (https://i.imgur.com/LyjkCWH.jpg)

I haven't yet investigated the make of the disk drives, and I also had difficulty getting both of them to latch. A metal bracket came out in the packaging, so it may have been damaged in shipping (FedEx actually packaged it themselves, so this isn't the fault of new_castle_j.

Now for the good stuff!

https://i.imgur.com/xL4xb4Ml.jpg (https://i.imgur.com/xL4xb4M.jpg)

(These boards have been posed for this picture, and aren't necessarily in the best order)

The machine has the following boards:

* Jade "The Big-Z" Z80 microprocessor board, JGZ80 RevC (1979)

https://i.imgur.com/IqNma8Nm.jpg (https://i.imgur.com/IqNma8N.jpg)

* Jade "The Memory Bank" 64K dyanmic RAM (1981)

https://i.imgur.com/zgAtP69m.jpg (https://i.imgur.com/zgAtP69.jpg)

* CompuPro Interface 4 3-channel Serial I/O w/ CENTRONICS and Universal Parallel Ports (1983)

https://i.imgur.com/9rgSmbUm.jpg (https://i.imgur.com/9rgSmbU.jpg)

* Jade "Double D" double density disk controller (1980)

https://i.imgur.com/130x4aMm.jpg (https://i.imgur.com/130x4aM.jpg)

The Z80 board also came with an RTC protoboard that the original owner (before new_castle_j) had created:

https://i.imgur.com/qY2zSbWm.jpg (https://i.imgur.com/qY2zSbW.jpg)

Thin IC socket extenders were stacked up to allow it to plug into the Z80 slot and hang on top of the board. As new_castle_j pointed out, modifications to the EEPROM or on the boot disk may contain code that interfaces with this custom, undocumented board. The board doesn't have it own dedicated Z80A--that processor is just extended up from the Z80 S100 board. The Jade Z80 board also seems to have some modifications done to it, but I haven't figured those out yet.

There's also this custom front panel board of unknown functionality:

https://i.imgur.com/JRmLxlWm.jpg (https://i.imgur.com/JRmLxlW.jpg)

Edit: And this board has an NCR 5380, which is a SCSI controller chip! Apparently this is a complete (or partially complete?) SCSI controller of some sort, with what looks like a 50 pin ribbon cable connector.

https://i.imgur.com/luxNxXqm.jpg (https://i.imgur.com/luxNxXq.jpg)

More and larger photos are available here: http://imgur.com/a/ZR4D9

In part 2, I'll describe what I've done with the machine so far, in my efforts to get it up and running.

new_castle_j
September 25th, 2015, 05:34 PM
Awesome! Looks like you've already cleaned it up nicely. I'm imagining plugging the hole in the front to the right of the floppy drives with front panel containing a dazzling array of blinkinlights and switches, setting a monitor on top of the case and calling it a Desktop machine.

MarsMan2020
September 25th, 2015, 09:12 PM
A few weeks ago I made a thread asking about the feasibility of owning and operating an S-100 bus computer. I learned about N8VEM, Zeta 2 SBC and alternative ECB cards, signed up for the N8VEM wiki, and discovered there's still a reasonably active homebrew community creating new ECB and S-100 bus cards.

And now, thanks to the great generosity of new_castle_j of this forum, I was able to obtain a homebrew S-100 bus computer with a few cards! He sent it to me for the cost of shipping, along with documentation, extra 8" disks, and an extra front panel project he had. He also very helpfully sent me a copy of the EEPROM from the Z80 board, as well as physical and digital copies of the machine's boot disk. I'm extreme grateful for this; thanks again!

That's so cool. I got my Vector MZ from a local friend.

Marty
September 26th, 2015, 03:48 AM
Hi All;

JNZ, You can't complain about the price.. And I am Not saying You have in any way..
Congratulations, the Wooden Case looks nice..
Also, a Thank You to New Castle for doing this for You..

THANK YOU Marty

retrogear
September 26th, 2015, 04:15 AM
Yes New Castle is very generous. He donated a couple systems to me for the price of driving and picking them up. It got me into the S-100 realm. Yours will be more of a challenge with a homebrew collection of cards.
Keep us posted !!

Larry G

JNZ
September 26th, 2015, 03:23 PM
I agree that the front area would look great with a custom panel, filled with switches, 7-segment displays, LEDs, and so on!

Part 2:

The first thing I did with the machine is photograph it, disassemble it, inspect everything, and clean it all with rubbing alcohol. I began to unsocket and reseat all the ICs, starting with the Z80 board, but stopped after I nearly broke a few leads by bending them. Even without breaking them, I'm sure I induced metal fatigue. As I don't have spare logic chips (yet), I stopped this plan before I got to the big chips, such as the EPROM. This may have been a bad idea, however...

I next inspected the PSU and checked some voltages. Everything seemed okay, with the transformer putting out 13.30 V, 28.89 V, and 9.23 V. These went into the rectifiers, and the bus itself received the rectified but unregulated DC power.

I started to compile a memory map of where the boards were registered in memory, so that I could understand what the EPROM code would be doing. I came up with the following:



Z80 EPROM - F000 - F3FF
Z80 board USART output addresses: 0x20 - 0x21

"Double D" FDD controller - FE00 - FBFF

CompuPro Interface 4 output addresses = 0x10 to 0x17
"READ" or "INPUT" ports
Relative port address

00 - Data port, read received data
01 - Status port, read UART status info
02 - Mode registers, read current UART mode
03 - Command register, read current commadn

"WRITE" or "OUTPUT" ports
Relative port address

00 - Data port, write transmit data
01 - SYN1/SYN2/DLE register, write sync bytes
02 - Mode registers, write mode bytes
03 - Command register, write command bytes


The EPROM dump begins like this:



; z80dasm 1.1.3
; command line: z80dasm -t -g 0 -a -l JADE.BIN

org 00000h

l0000h:
jp 0f59fh ;0000 c3 9f f5 . . .
jp 0f020h ;0003 c3 20 f0 . .
jp 0f5b8h ;0006 c3 b8 f5 . . .
jp 0f5c3h ;0009 c3 c3 f5 . . .
jp 0f5d0h ;000c c3 d0 f5 . . .
xor a ;000f af .
l0010h:
ld (00004h),a ;0010 32 04 00 2 . .
ld a,04eh ;0013 3e 4e > N
out (011h),a ;0015 d3 11 . . ; 0x11 appears to be CP4 SYN1/SYN2/DLE register


I couldn't figure out what's in F59F, F5B8, F5C3, or F5D0. F020 is 20 bytes into the EPROM. The F59F, etc., has to be memory mapped ROM, no? It makes no sense to jump to uninitialized memory. I may be wrong about where the FDD EPROM is mapped, or maybe CPU execution doesn't start at 100h. Maybe I'm missing data from 0h?

I put the Z80 board in the machine and began the process of figuring out how to tell what was going on. I ended up using the custom front panel, which only displayed all 1s for the address and bus lights. This led me to think the panel was malfunctioning, but inspection revealed no problems, and the board's logic seems very simple.

It looked something like this (but the CPU may have been in a different state):

https://i.imgur.com/vC6zuh6m.jpg (https://i.imgur.com/vC6zuh6.jpg)

This eventually led me to inspect the Z80 board again. And, oh no! The EPROM was in upside down. This is actually visible in the full size version of the picture (https://i.imgur.com/VBaUUrl.jpg) I took while cleaning the board, but it would take the eyes of an eagle to see it from the photo. I didn't notice it while inspecting it, sadly.

https://i.imgur.com/VBaUUrlm.jpg (https://i.imgur.com/VBaUUrl.jpg)

Question 1:

I don't know what happens when you insert an EPROM in this board backwards, but I'm sure it's nothing good. Is it still intact? Does it need reflashing? Is it fried? Is the entire board fried?

I reversed the EPROM and used the front panel to step through the CPU state and saw the following:

Run 1:


Address Data
00 00 FF ; RST 38H
FB F0 00 ; ?? (probably pushing SP on stack?)
FB EF 01 ; ?? (~PWR is high here, indicating DATA bus is invalid at the moment, I think)
00 38 FF ; In ISR, RST 38H
FB EE 00
FB ED 39 ;
00 38 FF
FB EC 00
FB EB 39
FB EA 00
FB E9 39
00 38 FF
FB E8 00


Run 2:


Address Data
00 00 FF
FB F6 00
FB F5 01
00 38 FF
FB F4 00
FB F3 39
00 38 FF
FB F2 00
EB F1 39
00 38 FF
FB F0 00
FB EF 39
00 38 FF
FB EE 00
FB ED 39


I didn't write down the machine state, and didn't know when it was doing a machine instruction fetch cycle or busy doing IN, OUT, or an interrupt.

Question 2
It would seem to me that the board is continually executing a RST 38H. What's at 0038H? Another RST 38H. Why? I'm not sure.

JNZ
September 26th, 2015, 06:20 PM
Some more things I noticed on the "Big Z" Z80 CPU board:

* C26 appears to have been clipped or broken off, perhaps accidentally or perhaps with a bad desoldering job. Same with C22. C26 is listed as 1.5 uF, along with a bunch of others, but the silkscreen is very different from the rest of those, and also isn't marked with polarity.

* Y1 is 4 MHz, not 16 MHz or 32 MHz

* The bus wire connector "L" is populated with a wire connector, as is "F," but no wire runs between them.

This leads me to believe that the manual I was able to get online doesn't reflect this revision of the board. Hopefully the DIP switch settings are the same as the manual.

It's also possible that these are part of the modifications necessary to get this custom RTC board to work.

JNZ
September 27th, 2015, 09:16 AM
I also found out that it's a 2716C EPROM, so I'll need a programmer that can deal with it, and possibly a replacement EPROM.

new_castle_j
September 27th, 2015, 03:36 PM
I'll send you another Eprom, or two, I see that there's also a newer version of the JGZ80 ROM image on Don Maslin's archive.

JNZ
September 27th, 2015, 03:42 PM
I'll send you another Eprom, or two, I see that there's also a newer version of the JGZ80 ROM image on Don Maslin's archive.

Thanks! You can contact me on email and I'll pay for the chips and shipping, if you wish. 2716 EPROMS and especially the programmers seem slightly costly.

I also did some research and found that the 28C16 should be a drop-in replacement for the 2716. I ordered two of those and an EEPROM programmer.

Does that mean that the 2716C EPROM is certainly fried? What is the machine doing when it keeps calling RST 38H?

JNZ
September 30th, 2015, 04:43 PM
In the past few days I've come to understand the existing code in the EPROM better, learning that it's (probably) trying to use the on-board USART to output system messages. I attempted to connect a USB serial port I've previously used on real RS-232C devices, only to have the machine now enter a state where it doesn't reset on power-on or reset. I've begun the troubleshooting process in the manual (thanks new_castle_j for finding the Rev. C manual for my "Big Z" board). I verified the 7805 VREG was putting out ~+5V (+5.36V), and then discovered that pin 6 of the Z80A wasn't receiving a 4 MHz clock. I'm investigating the clock generator portion of the circuit now, trying to identify what could be the cause. I'm not sure why this would manifest itself as soon as I tried to connect a serial port, however. When I connected the USART I triple checked that GND was among the signals I connected (TX->RX, RX->TX, and GND->GND), so that no voltage differential for GND would exist in the TX and RX lines.

I also commented that C22 was missing, and the manual describes errata where the C22 value should be changed, or it leads to strange reset operation. I added 1 uF aluminum electrolytic cap, as I don't have a tantlum of the same value at the moment. Hopefully this is okay.

Also, I previously described C26 being broken off--well, C26 is a 0.001 uF cap used in the oscillator circuit.

JNZ
September 30th, 2015, 05:09 PM
This whole area of the board is quite suspicious.

https://i.imgur.com/JygrqNVh.jpg (https://i.imgur.com/JygrqNV.jpg)

In its present state, both C26 (unpopulated) and C27 weren't connected. C26 appears to be a filter cap for the power rail of U21, a hex inverter (74LSO4N), but C27 seems far more important. It's a 0.001 uF cap that sits between two hex inverters, and without which one side of the 4 MHz crystal doesn't connect to anything at all. It appears that the copper annulus has delaminated from the surface of the PCB, perhaps due to handling when I put the board in. There's corrosion that's seeped under the solder mask, and perhaps the annulus was just barely making electrical contact for a long time now, and finally gave up the ghost. Note too the bottom lead below the annulus, which is folded over. Half that annulus is missing. Something's clearly gone horribly wrong on this part of the board! Too much heat when soldering? Contamination? Oxidation of the copper or whatever substrate holds it onto the PCB?

This is after my initial cleaning with rubbing alcohol. Although gentle and with a toothbrush, it's possible it aggravated the problem.

That glob to the left of the annulus is one lead for C26, and it's actually a via, if you can believe it. Gross!

JNZ
October 2nd, 2015, 09:45 PM
I received my Chinese EEPROM programmer and two AT28C16 EEPROMs. After much difficulty getting it working (it didn't play nicely with Windows 8, and one of the two EEPROMs refuses to clear the 64 bit for every cell, so the memory reads 0x40 when I try to clear all bits), I was able to reliably flash ROMs. I tried a number of times with the Jade System Monitor V4, as well as the modified ROM that came with it, before finally assembling the V2 version of the ROM myself.

https://i.imgur.com/bYwwwPmh.jpg (https://i.imgur.com/bYwwwPm.jpg)

Success!

Thank God for that front panel board. It's extremely helpful in debugging, especially because I don't have an S100 bus expander board yet.

JNZ
October 2nd, 2015, 09:53 PM
I forgot to mention that I had to make a few syntactical modifications to the Big Z Monitor 2.0A code to get it to compile with Z80ASM. On the off chance this saves someone some time, here it is:

http://pastebin.com/GpytdrXq

or

https://paste.ee/p/E9J58

new_castle_j
October 3rd, 2015, 06:25 AM
It's Alive!! It's Alive!!

Fantastic progress. Were you able to determine if the upside down EPROM got corrupted?

I see an option to "Load" (write direct into memory) in the Monitor code, I'm guessing that it is
expecting to see HEX character input at the console. If you can figure out how that works, you
may want to load in a memory diagnostic program and check out the memory board.
I've used the memdiag.asm and memdiag.doc files from https://github.com/ezet/i8080-emulator/tree/master/diag
You would just need to modify the console I/O parameters section, then compile into HEX. A terminal emulator program like TeraTerm would be able to transmit the HEX characters to the console, and once it's all written into memory, jump to H100 and run. One thing to be mindful of is if the Monitor program is expecting Intel HEX format or RAW HEX (without the checksum values), I'm guessing it would expect RAW.

JNZ
October 3rd, 2015, 07:27 PM
Fantastic progress. Were you able to determine if the upside down EPROM got corrupted?

Unfortunately my cheap Chinese programmer wasn't able to read the EPROM, so I can't do much with it yet. In theory this could be caused by a fried EPROM, but I can't determine that for sure unless I can find another 2716 (the FDD controller might have one).

Also odd is that the CPU board wouldn't read my EEPROM until I started poking around with my oscilloscope probe, and then it suddenly loaded valid data. Something must've been loose, even though I reseated everything. Not sure what was happening, but it's the first time I ever saw valid data on the data bus. The name of the game with this Z80 board is intermittent failures.




I see an option to "Load" (write direct into memory) in the Monitor code, I'm guessing that it is
expecting to see HEX character input at the console. If you can figure out how that works, you
may want to load in a memory diagnostic program and check out the memory board.

You read my mind. I had to figure out the code, but I learned that the load command works by taking an address in (two ASCII chars for HEX vals), a space, and then a repeating stream of sets of two chars, separated by spaces. The data is loaded into memory as you enter it. '#' terminates the program and returns execution to the monitor (if you haven't corrupted it).

Now that I've figured this out, I can compile that memory check (or write my own) and load it up. I'm not sure how to begin execution at an arbitrary address yet, but it should be simple enough to figure out in the ROM monitor code.

You're right about it being RAW HEX. Though I don't know what the Intel format looks like, I don't see anything in the load program to deal with special/metadata bytes in any way.

JNZ
October 4th, 2015, 03:46 PM
Memtest looks good!



MICROCOSM ASSOCIATES "SUPER MEMORY DIAGNOSTIC" VERSION 1.01 (C) 1979

TOP OF MEMORY=EFFF

MEMORY QUALIFICATION TEST IS IN PROGRESS

TEST MEMORY IN "AUTO" MODE (Y OR N)?y

TEST MEMORY IN "AUTO" MODE (Y OR N)?Y

TESTING MEMORY,FROM 1000 TO 2000
PASS=0001, TOTAL ERRORS=0000
RANDOM PATTERNS TEST
WRITE SATURATION TEST
GALLOPING PATTERNS TEST
-t
?
-T

TEST MEMORY IN "AUTO" MODE (Y OR N)?Y

TESTING MEMORY,FROM 1000 TO 2000
PASS=0001, TOTAL ERRORS=0000
RANDOM PATTERNS TEST
WRITE SATURATION TEST


The manual tests also seem to succeed just fine!

new_castle_j
October 5th, 2015, 06:22 AM
Wonderful, so now you have an operational computer, CPU, Memory, and I/O, just the basics, everything else is just peripherals. Floppy disk support on this machine is the next challenge I guess. You've made such quick work of everything so far, by the way, how did you deal with C26 and C27?

g4ugm
October 5th, 2015, 12:04 PM
By the way putting EPROM or most other chips in wrong way round invariable fries them, as it reverse polarity of voltage.

JNZ
October 5th, 2015, 05:30 PM
Wonderful, so now you have an operational computer, CPU, Memory, and I/O, just the basics, everything else is just peripherals. Floppy disk support on this machine is the next challenge I guess. You've made such quick work of everything so far, by the way, how did you deal with C26 and C27?

C26 I left unpopulated until I need to order a bunch of parts from Mouser, as it's just a small power cap for the HEX inverter*. C27 I repaired by bending the annulus back and reflowing the joint, trying to cover up as much of the exposed trace as I could. I also cleaned things up some more, to try and prevent any further corrosion. If water or water-based flux got under the soldermask, though, I'm not sure if the reaction will be stopped by simple cleaning.

I've learned that the front panel won't work with the FDD controller in place, perhaps due an issue covered in an errata memo from Jade. I could cut some traces on the FDD controller to make it compatible with that front panel, probably.

I agree about the FDD controller being the next to tackle. I used the V2 monitor to dump and disassemble the controller firmware, but it's long and complicated. I still don't understand what's at memory location F5B8-F5D0, which are called at the very start of the computer's modified V4 Jade ROM. According to how I've read the switches, the FDD controller is located at FE00-FBFF. This area of memory isn't called until the second instruction in the modified V4 ROM.

There *are* valid instructions extending partway into F5B8, but jumping to F59F makes no sense, as it's partway through an instruction.

If anyone's trying to follow along with WTF I'm talking about:

The Jade V2 monitor ROM I'm using: http://pastebin.com/WEMZFcBz

The modified Jade V4 custom ROM that was on the 2716 EPROM: http://pastebin.com/68W0qjgV

The disassembled contents of memory starting at F020: http://pastebin.com/4e9nsiHx

* Or it might also be part of a low-pass filter for that clock generator IC (U11? The Xeroxed schematic is fuzzy)

JNZ
October 5th, 2015, 05:50 PM
Oh you know what? I made a mistake disassembling the custom V4 ROM. I should've located it not at 0x0000, but at 0xF000. Then the function calls make a lot more sense.

http://pastebin.com/yBr80A4k

JNZ
October 5th, 2015, 09:10 PM
Oh snap!

Armed with the knowledge that the jumps listed in the custom V4 ROM were to the ROM itself, I began to make some serious progress. I found the serial code and discovered that it was modified to use the CompuPro 4 serial channel A, rather than the Big Z on-board USART. It also was using it at a zippy 19200 BPS! I flashed the custom V4 ROM back on and got it to print out the ROM monitor again.

I had no idea where to jump to actually start the boot sequence, so I looked for the embedded ASCII "Insert System Diskette" and found it in the disassembled code. I then figured out the call hierarchy and discovered the function that kicks everything off. I was then able to 'G' right to it.

Both drives are damaged in some way. The bottom one doesn't want to accept a diskette, and the locking mechanism on both is damaged, so I have to hold the door down. I swapped the cable, making the top drive the first one on the cable.

Here's the start of my log of my serial terminal session just now:



Jade Computer Products Monitor 2.4C

EFFF
* G F020

Insert System Diskette
Spider/Z 58k CP/M Ver 2.2 CBIOS Ver 3.3

/238WORK.LBL
A0>dir
/238WORK.LBL : MEX .COM : ZDEVT100.COM : NZCOM .CCP
ST238 .COM : HDFMT .HEX : NVDS .HEX : BIOSGEN .COM
SYSGEN .COM : FORMAT .COM : DOS58 .REL : BD04 .COM
CBIOS238.HEX : NOVA1A .HEX : CPM58B .BIN : NOVADOS .HEX
BGZRDS19.LBR : NVDIUPDT.LBR : CPM58 .BIN : CPM58 .COM
DOS .LIB : ZPATCH .COM : Z80CCP .HEX : NZCOM .LBR
NZCPR .LBR : FCP .LBR : MAC .COM : DATE .COM
MOVCPM .COM : CHKDIR10.COM : SAPZ11 .COM : RCP .LBR
NZ-DBASE.INF : CP .COM : DIR .COM : BOOT .COM
NZBLITZ .COM : STARTZCM.COM : DDT .COM : DU .COM
DUMP .COM : EDT .HLP : NZCOM .COM : NZCPM .COM
LOAD .COM : CPMA58 .BIN : PIP .COM : PRINT .COM
CPM .BIN : STAT .COM : SUBMIT .COM : UNERA .COM
UNSQ .COM : EX .COM : NZCOM .ZCM : XSUB .COM
ASM .COM : ERA .COM : MORE .COM : MLOAD .COM
SD .COM



I ran TYPE on a number of the HEX files to get backups of them (even though new_castle_j helpfully provided me with a full digital backup of the disk). I started running some commands, but NZCOM wanted to write a file back out (NZCOM.CCP), and since I didn't know what I was doing I stopped. I dont' know how to get files in and out of CP/M yet, so I don't want to screw anything up.

Just for fun, here's a pic of my current setup:

https://i.imgur.com/l1M7RqTl.jpg (https://i.imgur.com/l1M7RqT.jpg)

There's a Raspberry Pi back there, complete with the world's most ridiculous monitor for this application. (What I had laying around.)

JNZ
October 9th, 2015, 11:33 AM
I'm having two CP/M problems:

* The first drive shows up as A0> but if I try to CD to B: the system just hangs. CTRL-C doesn't perform a reset back to CP/M.

* Stat reports the A drive as R/W, but when I try to use PIP to write a file, I get an error:

A0>PIP PCGET.ASM=CON:[H]

Error, Disk A: Write Err
Fnc: 22; File: PCGET .$$$

I put a piece of masking tape over the notch cut into the bottom of the disk, so it should be R/W.

Does anyone know what's going on here?

deramp5113
October 9th, 2015, 11:55 AM
How much free space does stat show?

JNZ
October 9th, 2015, 12:58 PM
How much free space does stat show?

Sorry, I pasted this but overwrote it accidentally.



A0>stat
A: R/W, Space: 44k

new_castle_j
October 9th, 2015, 09:19 PM
* The first drive shows up as A0> but if I try to CD to B: the system just hangs. CTRL-C doesn't perform a reset back to CP/M.

In CP/M there isn't a CD command, to switch to drive B: just type B:

new_castle_j
October 9th, 2015, 09:26 PM
I also notice on the disk, a file called NZCOM.COM, might want to read up on that here: http://gaby.de/ftp/pub/cpm/nzcom.pdf

JNZ
October 10th, 2015, 11:01 AM
* The first drive shows up as A0> but if I try to CD to B: the system just hangs. CTRL-C doesn't perform a reset back to CP/M.

In CP/M there isn't a CD command, to switch to drive B: just type B:

Ah yes, that's what I meant

new_castle_j
October 11th, 2015, 05:33 PM
I've had trouble with masking tape over the notch, I had to switch to something heavier.

JNZ
October 11th, 2015, 07:35 PM
I've had trouble with masking tape over the notch, I had to switch to something heavier.

Hah, you won't believe it (well, you might), but switching to black duct tape worked. The crazy thing is I tried silver duct tape before the masking tape, and even went so far as to remove the drive and inspect the R/W detection mechanism. That's one insanely sensitive IR photodiode, or a very bright emitter.

I'm still no closer on the second drive, and it seems that having two drives is pretty essential to these systems.

Also, I'll note that I would've used electrical tape from the get-go, but my cat batted it somewhere and it's apparently lost forever.

DDS
October 12th, 2015, 03:57 AM
Hah, you won't believe it (well, you might), but switching to black duct tape worked. The crazy thing is I tried silver duct tape before the masking tape, and even went so far as to remove the drive and inspect the R/W detection mechanism. That's one insanely sensitive IR photodiode, or a very bright emitter.

I'm still no closer on the second drive, and it seems that having two drives is pretty essential to these systems.

Also, I'll note that I would've used electrical tape from the get-go, but my cat batted it somewhere and it's apparently lost forever.

Back in the day most disks came with black tape intended to be folded over the notches. Some had silver metallic looking tape. Both varieties worked. But at some point one company supplied red tape that turned out to be effectively transparent at infrared wave lengths. Just because you can't see through it......

JNZ
October 13th, 2015, 03:31 PM
Back in the day most disks came with black tape intended to be folded over the notches. Some had silver metallic looking tape. Both varieties worked. But at some point one company supplied red tape that turned out to be effectively transparent at infrared wave lengths. Just because you can't see through it......

The silver tape I used is pretty thick, so my guess is that there was enough IR light around the computer to reflect it into the sensor. At the time I used it the FDD was out in the open, rather than in the case. The black worked much better, although I started getting write errors after writing just a few lines.

JNZ
December 5th, 2015, 10:50 AM
I still haven't solved the issue with one of the two floppy drives, but I did repair a broken component in an interesting way. On loading a disk the drive fires a solenoid that pushes a plastic spring-loaded bracket down onto the surface of the disk. This pushes on it firmly enough to make the magnetic disk rest against the head. On the malfunctioning drive this piece was held on with a twisty-tie and some cracked superglue, requiring me to manually move the head load armature when I was testing it.

The old bracket looks like this:
http://i.imgur.com/y0dbTzyl.jpg (http://i.imgur.com/y0dbTzy.jpg)

I fired up Solidworks and copied the design of the original bracket, then had it 3D printed at Shapeways. It came out great:

http://i.imgur.com/yvC4U6hl.jpg (http://i.imgur.com/yvC4U6h.jpg)

http://i.imgur.com/V99uBV2l.jpg (http://i.imgur.com/V99uBV2.jpg)

I did make a mistake and didn't match the original exactly:

http://i.imgur.com/M8f7qb5l.jpg (http://i.imgur.com/M8f7qb5.jpg)

...but I decided to have it printed anyway, as it was just a prototype. I found out that the plastic is far lighter and weaker than the original injection-molded plastic, so I've made another revision and sent it off to be printed. Although it would still work as-is, I fixed the width issue that makes it not match the original exactly, and reinforced some areas to hopefully make it stronger than the original.

The printing cost was less than $6, though shipping from Shapeways is $5.

JNZ
December 5th, 2015, 10:54 AM
Here's a glamor shot of the new revision in Solidworks:

http://i.imgur.com/y9ErtGDl.png (http://i.imgur.com/y9ErtGD.png)

new_castle_j
December 5th, 2015, 04:24 PM
Hey, that's really really cool. I didn't realize that 3D printing was economical enough for this kind of stuff. I suppose the biggest investment is the time it takes to figure out how to run the software and input the measurements.

JNZ
December 5th, 2015, 10:35 PM
Hey, that's really really cool. I didn't realize that 3D printing was economical enough for this kind of stuff. I suppose the biggest investment is the time it takes to figure out how to run the software and input the measurements.

There's definitely a learning curve, but I've found that learning 3D software continually pays dividends. With YouTube and free software like Blender there's basically nothing stopping anyone from learning it. Solidworks is definitely one of the industry standard tools out there, however, and if you can't find a trial there are probably some educational options. (I think you have to buy the full thing if you sell your designs, however.)

Once you realize you can 3D print things, you start finding uses for CAD knowledge everywhere. Cars, home furnishings, replacing one-of-a-kind fixtures or computer parts; one of my projects is to design a custom throttle bracket for my lawn mower, as the internal governor broke and it now requires manual throttle adjustment. It's like we're living in the future, being able to do this.

MarsMan2020
December 7th, 2015, 10:12 AM
There's definitely a learning curve, but I've found that learning 3D software continually pays dividends. With YouTube and free software like Blender there's basically nothing stopping anyone from learning it. Solidworks is definitely one of the industry standard tools out there, however, and if you can't find a trial there are probably some educational options. (I think you have to buy the full thing if you sell your designs, however.)

Once you realize you can 3D print things, you start finding uses for CAD knowledge everywhere. Cars, home furnishings, replacing one-of-a-kind fixtures or computer parts; one of my projects is to design a custom throttle bracket for my lawn mower, as the internal governor broke and it now requires manual throttle adjustment. It's like we're living in the future, being able to do this.

I printed some S-100 card ejector levers on a Makerbot. I had to make the design 2x as thick as the original part to make them strong enough to hold up, but they work fine.

JNZ
February 11th, 2016, 07:18 PM
I was ordering a VersaFloppy II board from Herb Johnson when he mentioned that it might be worthwhile to put information about the custom oak case of my computer up online. Rather than settle for just pictures, I decided to capture it in CAD software and create blueprints that others can freely use and modify:

http://i.imgur.com/n8j9FOBh.png (http://i.imgur.com/n8j9FOB.png)

http://i.imgur.com/HF9aHEzh.png (http://i.imgur.com/HF9aHEz.png)

From these anyone could use this as a template for their own enclosure, plus it'll serve as a good historical record for this system.

You can currently view all the blueprints here: http://imgur.com/a/jRElH

JNZ
February 11th, 2016, 07:31 PM
Some more Oaken Beast updates...

This is how the reinforced head load bracket came out for the floppy drive:

http://i.imgur.com/kK1clydl.jpg (http://i.imgur.com/kK1clyd.jpg)

And I designed a replacement for the latching mechanisms, reinforcing it in the process to hopefully prevent them from breaking:

http://i.imgur.com/jUMFAV6l.png (http://i.imgur.com/jUMFAV6.png)

This bracket (broken on both drives, but in different ways) would prevent the drive from staying closed on its own, requiring me to wedge something of just the right size in, which was quite inconvenient and might've been affecting reliability. You can kind of see the old brackets here (as well as the missing faceplate from one of the drives):

http://i.imgur.com/tb8ZKspl.jpg (http://i.imgur.com/tb8ZKsp.jpg)

If you look closely you can see that sometime in the distant past the original owner fixed the latch by using two tiny machine screws and a little piece of metal, which let it attach to the pin that it rotates around. I'm sure glad 3D printers are so readily available these days! It only cost me $6 per replacement latch, plus shipping.

MarsMan2020
February 11th, 2016, 09:04 PM
Love the Oak case. I've been thinking of doing a hobby case kit out of CNC-routed wood or phenolic, which could be shipped flat-pack and glued together by the builder. Custom metal cases for S-100 systems tend to be costly to fab AND costly to ship.

JNZ
February 11th, 2016, 09:21 PM
Wood seems fairly heavy to me to ship, but it's so much more flexible in terms of its ease of creation and modification. Is it cost-effective to use a CNC for cases like that?

When people look for new cases, do they want something that can fit only old gear, including those massive linear power supplies and 8" drives, or would they like something with a modern S-100 main board and space only for 5 1/4" or 3 1/2" drives? Or maybe even an external floppy disk drive enclosure. If you used modern SMPS I bet the assembled thing could be nice and light too.

Instead of glue (or in addition to it) you might be able to get fancy and route some dovetail joints or mortice and tenons. The end-user could just tap the case together.

Have any designs sketched out?

MarsMan2020
February 11th, 2016, 09:47 PM
Wood seems fairly heavy to me to ship, but it's so much more flexible in terms of its ease of creation and modification. Is it cost-effective to use a CNC for cases like that?

When people look for new cases, do they want something that can fit only old gear, including those massive linear power supplies and 8" drives, or would they like something with a modern S-100 main board and space only for 5 1/4" or 3 1/2" drives? Or maybe even an external floppy disk drive enclosure. If you used modern SMPS I bet the assembled thing could be nice and light too.

Instead of glue (or in addition to it) you might be able to get fancy and route some dovetail joints or mortice and tenons. The end-user could just tap the case together.

Have any designs sketched out?

There's several websites that offer laser-cut or CNC routed parts (similar to the 3D printed part sites). Dovetails might be an option as well.

I was thinking room for an 18 to 22 slot motherboard, with space next to it for 2 half-height 5.25" drives and modern switching power supplies. So geared towards people building with boards like the S100Computers set. Replaceable panels front and back in case a front panel / I/O ports are desired.

KC9UDX
February 11th, 2016, 09:49 PM
Draw it up and talk to some local fab shops, preferably with a laser. It's not terribly expensive.

JNZ
February 24th, 2016, 06:38 PM
My 3D-printed disk drive latches showed up the other day, and I just tested one out tonight. They work perfectly and feel extremely sturdy!

https://i.imgur.com/g08eI9pl.jpg (https://i.imgur.com/g08eI9p.jpg)

https://i.imgur.com/YTEi7qfl.jpg (https://i.imgur.com/YTEi7qf.jpg)

The hole should fit an LED, but I don't have a solution for the lens yet. I was planning on just finding an LED with a flat top and a diffuse lens, even though it won't look 100% the same as the original.

MicrocomputerSolutions
February 25th, 2016, 01:44 AM
Just use a regular round top led that fits in the hole.

Early Shugart Floppies used a flat top lens like your Siemens, but switched to a standard LED, eliminating the lens.

MicrocomputerSolutions
March 6th, 2016, 09:24 PM
Did you receive the eBay drive, and did it work?

JNZ
October 12th, 2016, 06:25 PM
>Did you receive the eBay drive, and did it work?

I forgot to update this post. I did, and it did!

I'm debugging my Jade 64 K Dynamic RAM and Jade Big Z boards, and I suspect that I might have an issue with the integrity of my dynamic RAM. Months ago when I first did a memory test things looked okay, but I ran into issues recently that were resolved by swapping in a static RAM board.

Here's a captured waveform representing the RFSH* (pin 66) signal in my S-100 system with my Jade Z board:

http://i.imgur.com/HOPAMTH.png

There's a significant DC bias. The frequency is .66667 MHz.

I swapped in a Cromemco ZPU board and recorded the same pin:

http://i.imgur.com/5j3qEwp.png

There's an irregularly timed signal (possibly caused by the CPU executing unknown code?). The DC bias is removed. The signal itself exceeds the 5V logic level, which I wasn't expecting.

My Jade 64K board takes the RFSH* line and puts it directly into a 74LS04 Hex Inverter, with no cap to remove DC bias. The 74LS04 DS says that the maximum voltage for a LOW level input is 0.8 V. At 4.16V it would seem this chip would never output anything but the inverse of a HIGH signal. Going on this logic I probed the output of this inverter while using the Cromemco board:

http://i.imgur.com/RLjPF2z.png

And then with my Jade Big Z:

http://i.imgur.com/Cxvjt8U.png

It would appear then that this board would never get proper refresh signals from the CPU.

There is one other consideration: the memory board provides a jumper that switches between using the output of this inverter and some other circuitry. It's currently set to use the useless signal originating with the Big Z board. The other setting seems to be useful only if you have an 8080 CPU, so it's currently in the only position I can use.

This is the second faulty signal that my Big Z board has generated. The previous one was caused by a delaminated via in the CPU clock circuitry.

Dawsoca
October 12th, 2016, 11:12 PM
I read your adventures with the Jade boards and it inspired me to get my 20 year old Jade Big Z and Jade Memory Bank working. I haven't got all the wrinkles worked out yet, but the Big Z boots to the Monitor and works with the Memory Bank. From your description I would look at U6(74LS367) and U15(74LS04) on the Big Z board to see if the Refresh signal is present on pin#11 of U6. U6 may be bad or never enabled by U15. You could also ohm out the traces from S100 Pin66 to U6 pin#11 and then to the Z80. I enclosed a Rigol capture of the refresh signal off pin#11 or U6.33795