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IMSAI 8080 noob, how to use?

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  • telemonster
    replied
    OKAY! MORE PROGRESS (And problems)! Much thanks to all for advice!

    Over on the #vc IRC Glitch gave me some advice that filled in a few holes as well.

    So, using the 88-2SIO (AMON) board I abandoned loading the data via sending it into the user input hex stuff (EN xx xx xx xx) and uploaded the .HEX file for PC2DISK.HEX from deramp.com downloads.

    I put the Northstar MDC-A4 back in, and hooked up the external 5.25" Northstar Drive. My friend SuperSoaker built out the hard sector to soft sector emulator kit for me while I was finding a floppy ribbon (no twists). I have the kit all together and that is now in-line with the drive. I tested for the ground side of the ribbons to make sure ribbons were all connected in the proper direction before powering any of it. The external floppy is blowing fuses, so something is probably dead on the PSU board. It's two linear regulators and a transformer, I will troubleshoot later. Hooked drive up to a PC power supply for now and it seems to be working fine. Might replace the two regulators with modern DC-DC converter type keeping the original PCB but shedding some of the heat.

    When I "EX E800" I get disk seek, so that is good. If I set the head position inwards, and do that it returns to home position. Head movement is there and drive seems to be talking to the controller.

    After ASCII upload (I am set a 4800 BPS, 8 N 2 ) the PC2FLOP.HEX or whatever that transfer utility is, I "EX 0100" and it runs! I say drive 1, and somethings it gives a sector 0 seek error. Drive does give red light. Normally if I try it a 2nd time it's A-OK and proceeds.

    At first I spent a lot of time trying to upload the NorthStar DOS .NSI image patched for Altair serial board... lots of errors, but I was using Minicom under Linux. I moved to Hyperterminal on an older XP laptop with an onboard serial interface and it sends without errors.

    What happens is it transfers till about 100 blocks, or 12-13K and then I see the disk drive in-use LED come on. The drive spins for a short bit then turns back off. The XMODEM Xfer hangs when this starts, and never resumes.

    Going to see how to peek at what is on the floppy disk.

    I feel like I'm close to getting Northstar DOS And CP/M disks written once I figure out what isn't happening right with the floppy drive.

    Leave a comment:


  • telmnstr
    replied
    Originally posted by smp View Post
    Lots of software and documentation available via dermal.com:

    https://deramp.com/downloads/

    smp
    Oh wow, NorthStar DOS for IMSAI even.... Interesting!!! Would have to re-patch it for Altair SIO I assume.

    Leave a comment:


  • telmnstr
    replied
    Originally posted by smp View Post
    The Altair Loaders and BASICs query the front panel switches to indicate which SIO port to use for communication to the terminal.
    IIRC, after loading and prior to running, you must set all address switches to 0, except for A12 set to 1, to indicate that you are using the 88-2SIO.

    HTH

    smp
    AH HAH! Okay, that gives me hope. I shall try again, there is no way I had A12 set high.

    Much thanks, will attempt and report!

    Leave a comment:


  • telmnstr
    replied
    Originally posted by Dwight Elvey View Post
    If the reader loads at 0, the BASIC is likely some place else. How do you load the BASIC without the loader?
    Dwight
    Ah the serial board has a ROM monitor that allows you to write values into memory, dump memory listings, and some other things. What I did was use a script or utility from Linux to convert the Altair BASIC binary into format compatible with the ROM monitor entry and then shove it into RAM over serial starting at 0000.

    Then execute at 0000.

    Leave a comment:


  • telmnstr
    replied
    Originally posted by BillGee View Post
    There is "an app" for that.

    Circuit board ejectors lever against the top of the card cage. They are very inexpensive, but shipping can be a killer. Maybe try to find something with free shipping in eBay?

    https://www.mouser.com/ProductDetail...FRKu9Kag%3D%3D

    I just realized it looks like I have two accounts on here, one as telmnstr and one as telemonster. That would explain why messages I thought I sent were missing a while ago.

    I am familiar with those, but most of the boards in my system are missing the holes they would mount in. I guess I could drill them but would be paranoid it would rip through the fiberglass board.

    Now that I've moved on from the original serial card I'm not swapping cards as much.

    Leave a comment:


  • smp
    replied
    Lots of software and documentation available via dermal.com:

    https://deramp.com/downloads/

    smp

    Leave a comment:


  • smp
    replied
    The Altair Loaders and BASICs query the front panel switches to indicate which SIO port to use for communication to the terminal.
    IIRC, after loading and prior to running, you must set all address switches to 0, except for A12 set to 1, to indicate that you are using the 88-2SIO.

    HTH

    smp

    Leave a comment:


  • Dwight Elvey
    replied
    If the reader loads at 0, the BASIC is likely some place else. How do you load the BASIC without the loader?
    Dwight

    Leave a comment:


  • BillGee
    replied
    Originally posted by JonB View Post
    Oooh serial comms, that old chestnut. Use the 'scope to determine where the signal breaks - tracing forwards from the UART with reference to the schematic. Maybe it is set up for hardware handshake? What's the BAUD rate (etc)? Do you have the manual?
    I would look for hardware handshaking first.

    My first computer was a SWTPC 6809 built from a kit. It refused to do anything. Everything pointed to a defective serial interface card. I was packing it up to send it back for service when I noticed an overlooked slip of paper in the box. SWTPC had changed the design of the board and the new one expects hardware handshaking by default. One small jumper wire later and I was running.

    Leave a comment:


  • BillGee
    replied
    Originally posted by telemonster View Post
    Also, the cards are very very very difficult to remove. Any tips? I was thinking of looping something underneath a card on both sides then pulling upwards?
    There is "an app" for that.

    Circuit board ejectors lever against the top of the card cage. They are very inexpensive, but shipping can be a killer. Maybe try to find something with free shipping in eBay?

    https://www.mouser.com/ProductDetail...FRKu9Kag%3D%3D

    Leave a comment:


  • telmnstr
    replied
    Okay, some updates...

    I bought a 88-2SIO serial/rom monitor board and it works. I am able to fill the memory and read it back fine. I have serial access that is similar to the Altair.

    So I tried so use some linux-fu / shell script to take the Altair BASIC and feed the hex over serial into the RAM of the system. But when I execute it doesn't seem to run (no serial output.)

    IIRC there is a loader that is often used first, that in turn reads a paper tape or cassette (if not in ROM.) Is there any kind of padding or execute address offset that is usually used?

    I feel like I am close to successfully executing something on it.


    I am also interested in finding NorthStar DOS floppy setup to work with the Altair serial port address, either on a hard sectored 5.25" floppy or a not hard sectored one (I have a board that is supposed to emulate the hard sector timing pulses.)

    Thanks

    Leave a comment:


  • telmnstr
    replied
    Hello! I made some progress... but still have one burning question.

    I bought the 88-2SIO board which has serial ports and a ROM monitor. I dropped that in my IMSAI and everything seemed to work no problem when I execute the ROM. I filled RAM and read the RAM back and it looked like it was behaving.

    The serial board is an Altair clone, so it should be compatible with Altair BASIC. I so took the Altair BASIC binary and converted it, then ASCII upload it into the ROM monitor (had to slow things way down.) It doesn't seem to execute though? It's been a few weeks since I've touched it but I started at 0000.

    I noticed that in the Altair world they would do a loader, then use the loader to read the program off of tape. Does this mean that jamming the binary into RAM there is some other start point?

    Progress is happening...

    Leave a comment:


  • DeltaDon
    replied
    You might try jointing the S-100 Google Group since they might be able to supply a copy of a ROM for your system that allows it to talk to the serial port.

    Leave a comment:


  • Dwight Elvey
    replied
    To bad you don't have a Polymorphic video card. It also has a parallel input port that is designed to work with a parallel keyboard. There are parallel port boards for the S100. As I recall, some of the serial cards also had a parallel port on them.
    There are also methods of changing 360k disk into hard sectored disk, to work with the N* controller, without the sector creating hardware.
    As for keyboards, it is possible to make a simple I/O to take a AT type keyboard and use it. It would take a lot of the processors time and memory resourses to do this but it is possible. It is better to use a separate processor as it typically done in a PC where a 8035 ( as I recall ) does the work of making characters. There are also several examples using various small processors on gethub as well.
    There is also no reason one could not just stay with the serial I/O. I often use my laptop as a dumb terminal, with the ability to download and up load data.
    Dwight

    Leave a comment:


  • Hugo Holden
    replied
    Originally posted by telemonster View Post
    Hello all!

    I've owned an IMSAI 8080 for a number of years now -- but I have never quite figured out how to use it / get it working.


    There is a video output board. Processor Technology VDM-1. I have tried it with and without it

    There is a serial IO card that also includes a monitor ROM. It also has a cassette interface as well.

    Any pointers appreciated. I'm a S-100 newbie, and it's been kind of a long journey piecing together how this is supposed to work.

    Maybe I can help because I don't know too much about the IMSAI. But I do know a little about Northstar disk controller cards and the VDM-1. (I only learnt something about S-100 computers after I got a Sol-20)

    From what I can gather the IMSAI 8080 (and I'm sure I'll be corrected if wrong by forum members) was intended to run with a dumb terminal, via the serial link. So that terminal provided the video display for the text and the keyboard for the operator.

    The VDM-1 card on the other hand was like 1/2 of a dumb terminal, in that it provides the text display as a composite video output for a monochrome monitor (or modified TV set). The circuitry in the VDM-1 is practically identical to the video text generator in the sol-20 computer. Also, along with that in the sol at least, it has a keyboard and an elaborate monitor ROM called a personality module which has the firmware which supports the keyboard, I/O functions for the serial/parallel ports, the tape interface and the video circuitry.

    Therefore, the only reason I can think of why you would find a VDM-1 in an IMSAI 8080, would be if somebody was trying to make the computer independent of the need for a dumb terminal. If that were the case, it would seem there would also have to be some sort of keyboard interface and a suitable monitor rom, running the firmware to support it. I have no idea if this hardware/firmware exists in your IMSAI 8080 or on another s-100 board in there, but I'm sure others who do know will shed light on it.

    The Northstar disk controller card, can most likely also be used with more modern 5.25" 360kb disk drives (preferably direct drive types as they are more stable), and soft sectored discs, if you get/buy Mike Douglas's virtual sector generator (VSG) board, which is just a small pcb that plugs in line with the drive cable.

    For my SOL-20 I put two YD-580 drives in a box, with Mike's VSG:

    http://worldphaco.com/uploads/EXTERNAL_DUAL_5.pdf


    The Northstar card has all the firmware on it (in the way of three OTP roms) to work, so you don't have to write anything to get the disk drives up and running, but you need the CP/M 2.2 version software on a 5.25" disk which is configured to work with it, and Mike Douglas might be able to give you some pointers on how to do it after you get the VSG. So probably, unless you want to be stuck with the hard sectored media, the first plan would be to get the VSG and a suitable disk drive unit. And try to get the VDM-1 working, but like I say I'm not sure (have no idea) how the keyboard fits into the equation with the IMSAI computer, or if you will be stuck with the need for a dumb terminal.

    The cassette interface will be very straightforward, its probably the CUTS one from Processor Technology.

    Leave a comment:

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