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IMSAI 8080 noob, how to use?

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  • Dwight Elvey
    replied
    Getting an extension card is what you want. In places where I need to monitor several places with the scope but have no extension card or easy access, I tack wire wrap wire onto the PC board. I may have as many as 10 wires at times. I lead them out to a piece of cardboard and tape them down. I use a sharpie to note which is which. It helps to have a large spool of wire to use. I just got about 5 lbs worth of 4 wire uncovered telephone wire. I'll be using that on my next project repair.
    You might look at making something simple from plumbers tape. You want a loop at the bottom that can be supported from both sides of the board. Maybe a screw that will catch one of the holes on the loop of plumber tape to be able to pull up on both sides at the same time. Then, a wood handle with two of these loops for both ends of the board.
    One might give some more though to the way to catch the other side of the loop than a screw but you still need the something to separate it when you lower it around the board and easily catch it to the hooked piece of tape.
    Dwight

    Leave a comment:


  • telemonster
    replied
    Thanks both for the information!

    I finally got my other laptop to dig up the info. It's a National Multiplex / Computer Aid 2SIO.
    Glitch hooked me up with the manual a while ago, props to him:
    https://users.757.org/~ethan/pics/ge...Aid_2SIO-R.pdf

    I need to probe at it some more. One issue is I can't really probe the card with it in system as there isn't enough room. I can pull out the video board (I hooked up to it before and never saw output, although I did just look at the manual for it yesterday online.)

    I have some 5V TTL Serial dongles and such for my micro-controller stuff. I will prod at it again.

    IIRC I didn't see output from the UART, but the last troubleshooting was a while ago. I tend to rotate through back burner projects and now this one is dead center and progress must me made

    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?

    Thanks again

    Leave a comment:


  • JonB
    replied
    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'd start by pulling as many cards as possible to leave a minimal configuration, then try to get the monitor talking to the serial port.

    Did you observe output from the UART before replacing the line drivers? You could use a USB RS232 adapter like this one https://www.ebay.co.uk/itm/323657771578 to connect direct to the UART input / output pins if the drivers are suspect.

    Leave a comment:


  • Dwight Elvey
    replied
    The monitor ROM should show what is needed to connect a serial board. It should also have notes on what is needed for the N* board. You'd most likely need to use a 5.25 inch floppy drive with a direct drive. The belt drive ones don't maintain enough consistent speed to work with most hard sectored adapters. Of course, it is possible to make hard sectored disk from soft sectored. You'll still need 360K disk and drive. You can not use 1.2M drive or 1.2M disk easily.
    Most people implemented CP/M. There are books on setting up CP/M on a machine and most of the *.COM files you'd need are on the web. You'd likely have to write your own BIOS level code. Many SOL users had CP/M on their machines using the N* controller. One might look for them to see what can be had.
    First it would be useful to get the serial to work. I recommend getting one of the RS232 light boxes to figure why your serial isn't working. I have no idea what monitor you have and what it was set up for.
    Dwight

    Leave a comment:


  • telemonster
    started a topic IMSAI 8080 noob, how to use?

    IMSAI 8080 noob, how to use?

    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.

    My system has 6 x 8K boards in it, that seem to be addressed properly.

    There is a Northstar Floppy controller which I'm ignoring for now, it's hard sectored disks. I did buy some widget that is supposed to emulate the hard sectoring but haven't assembled or touched it yet.

    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.

    I have hooked a terminal up to it, and from the manual for the serial IO card it says to execute at C800. I have done this, and the lights on the front panel start to run. Code is executing.

    But I never see any serial output on the terminal. I'm supposed to get a prompt.

    I've replaced the line driver chips after the UART, but no difference. I've watched serial output with an oscope and I don't think anything comes out of the serial port.

    I walked thru examining the first bytes of the monitor ROM versus the program listing in it's manual and it looked good, so I am able to see that.

    Any thoughts as to what next? I pulled out the card that has the composite video output. I hooked up a monitor to it in the past and don't remember seeing a prompt there. The system came complete to me, but no floppy disks.

    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.
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