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 1: Remain civil and respectful

There are several hundred people who actively participate here. People come from all different backgrounds and will have different ways of seeing things. You will not agree with everything you read here. Back-and-forth discussions are fine but do not cross the line into rude or disrespectful behavior.

Conduct yourself as you would at any other place where people come together in person to discuss their hobby. If you wouldn't say something to somebody in person, then you probably should not be writing it here.

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Rule 2: Stay close to the original topic being discussed
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Rule 3: Contribute something meaningful

To put things in engineering terms, we value a high signal to noise ratio. Coming here should not be a waste of time.
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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.

Reporting problematic posts

If you see spam, a wildly off-topic post, or something abusive or illegal please report the thread by clicking on the "Report Post" icon. (It looks like an exclamation point in a triangle and it is available under every post.) This send a notification to all of the moderators, so somebody will see it and deal with it.

If you are unsure you may consider sending a private message to a moderator instead.

New user moderation

New users are directly moderated so that we can weed spammers out early. This means that for your first 10 posts you will have some delay before they are seen. We understand this can be disruptive to the flow of conversation and we try to keep up with our new user moderation duties to avoid undue inconvenience. Please do not make duplicate posts, extra posts to bump your post count, or ask the moderators to expedite this process; 10 moderated posts will go by quickly.

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 RAM board

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    Imsai RAM board

    Hi all !

    I recently acquired an Imsai 8080 machine and I'm
    looking to get it up and running.

    It came with only a CPU board 8080 rev-4 and a Expandoram II
    memory board. I also picked up a Microbyte 32k board from ebay.

    I'm not sure if either one of these boards are compatible with the 8080.
    I know from the docs I read about the Expandoram it mentioned z80 so
    maybe it wont work with my system (bought as-is)

    The problem I'm having is that I can't deposit to memory and
    examine it back, the data LED's are all high no matter what I do.

    So I'm wondering if its a memory issue or something else. I've verified
    voltages and sniffed around with a logic probe (thinking a bad IC
    on the front panel pulling the data bits high)

    To sum it up, since the CPU board doesn't have any memory, I guess
    I need to know if the memory boards I have are compatible. Maybe
    there both bad. I don't want to chase my tail, been doing that for a week

    Anyone have a suggestion or perhaps a static ram board for sale
    so I can continue debugging this machine.

    I also posted to the s100computers forum with a bit more
    detail earlier in the week.


    I have an Expandoram II working with an 8080.
    It is a Polymorphic CPU board though. The Expeandoram
    has the built in refresh so doesn't need the Z80's refresh.


      I guess I don't understand the dip switch settings for the expandoram II.
      How should I set the switches for my Imsai, just one memory board installed.
      The board is set up for 64k. I'm not sure I understand what the 'banking' is all
      about, if someone could explain.


        Banks are use when you want more than 64K on the bus.
        The banks are controlled by one of the I/O ports ( I forget
        which ).
        You expect to use all of the memory so I'd say that you'd
        want to turn it all on. I think for that board, there are 4
        16K banks.
        If you have ROM in your system, I believe the board uses
        the Phantom signal to disable the RAM for that part of
        memory so that it doesn't conflict.


          Originally posted by Dwight Elvey View Post
          Banks are use when you want more than 64K on the bus.
          The banks are controlled by one of the I/O ports ( I forget
          which )
          40H is often used.


            In the infamous words of Gene Wilder... 'It's Alive !'

            Today I received a Godbout 8k static RAM board from ebay and a bunch of parts
            from digikey & jameco. I replaced all the caps on the MPU, a few bus driver IC's
            and the 8212 IC. I was able to deposit & examine data into memory & verify !
            I toggled in a 'chase LED' program I found on the net by Lawrence Woodman.

            I must have toggled that program in about six times before I realized that my first
            deposit into memory should have been a deposit, and not a deposit next. YeeHaw,
            the program worked ! I'm so excited I hated to turn the dang thing off.

            Here's a link to a short video I made. It's an .avi file and it's the first vid I've
            done so if it's to long or big, sorry about that.


            Well it's late and I've been up since 4AM (had to take the girlfriend
            to the airport so she could see her ma in Sacramento) So I'm gonna
            call it quits ! If you would like to see my other hobby check out;


            Thanks guys !