Forum Rules and Etiquette

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This forum is part of our mission to promote the preservation of vintage computers through education and outreach. (In real life we also run events and have a museum.) We encourage you to join us, participate, share your knowledge, and enjoy.

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Rule 4: "PM Sent!" messages (or, how to use the Private Message system)

This forum has a private message feature that we want people to use for messages that are not of general interest to other members.

In short, if you are going to reply to a thread and that reply is targeted to a specific individual and not of interest to anybody else (either now or in the future) then send a private message instead.

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Why do we have this policy? Sending a "PM Sent!" type message basically wastes everybody else's time by making them having to scroll past a post in a thread that looks to be updated, when the update is not meaningful. And the person you are sending the PM to will be notified by the forum software that they have a message waiting for them. Look up at the top near the right edge where it says 'Notifications' ... if you have a PM waiting, it will tell you there.

Rule 5: Copyright and other legal issues

We are here to discuss vintage computing, so discussing software, books, and other intellectual property that is on-topic is fine. We don't want people using these forums to discuss or enable copyright violations or other things that are against the law; whether you agree with the law or not is irrelevant. Do not use our resources for something that is legally or morally questionable.

Our discussions here generally fall under "fair use." Telling people how to pirate a software title is an example of something that is not allowable here.

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New user moderation

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New users also have a smaller personal message inbox limit and are rate limited when sending PMs to other users.

Other suggestions
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IMSAI 8080 noob, how to use?

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    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?

    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.


      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?
      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.


        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.


        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!


          Originally posted by smp View Post
          Lots of software and documentation available via

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


            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 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.