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Thread: IMSAI 8080 noob, how to use?

  1. #11

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    Quote 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

  2. #12

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    Quote 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.

  3. #13

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

  4. #14
    Join Date
    Oct 2011
    Location
    Bedford, NH, USA
    Posts
    1,628

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    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

  5. #15
    Join Date
    Oct 2011
    Location
    Bedford, NH, USA
    Posts
    1,628

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    Lots of software and documentation available via dermal.com:

    https://deramp.com/downloads/

    smp

  6. #16

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    Quote 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.

  7. #17

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    Quote 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.

  8. #18

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    Quote 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!

  9. #19

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    Quote 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.

  10. #20

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    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.

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