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.

This forum has been around in this format for over 15 years. These rules and guidelines help us maintain a healthy and active community, and we moderate the forum to keep things on track. Please familiarize yourself with these rules and guidelines.

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.

This should be obvious but, just in case: profanity, threats, slurs against any group (sexual, racial, gender, etc.) will not be tolerated.

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.

Here are some obvious examples of when you should not reply to a thread and use the PM system 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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Cromemco System Three restoration - initial questions

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    Cromemco System Three restoration - initial questions

    I'm at the early stages of attempting to restore a Cromemco System Three. This thing is built like a tank. It's the second-heaviest S100 machine that I own.

    This one is fitted with a ZPU / 64KZ / TU-ART / 16FDC (fitted with RDOS 2.01 PROM) and a single PerSci 299 drive.

    It came to me with about 10 boxes of hard-sectored 8" floppy drives. I don't now for certain whether they belong to this system. They were stored in close proximity to it (but also with many other vintage computers). Most of the disk labels identify a typesetting program, font names etc. None of them explicitly mention Cromemco, CDOS, CP/M, etc.

    Sadly its been subject to rough storage and handling, so all rear panel fuse holders and Drive 1's front panel eject button have been sheared off. I'm currently fixing this damage, rejuvenating power supply capacitors (and replacing with that has suffered physical leakage), etc.

    I've found some helpful documents on Bitsavers and John's site.

    So here are my initial questions:

    1. Does the 16FDC/RDOS 2.01 ROM support soft-sectored 8" disks in the PerSci 299? If so, presumably I can download a CDOS 8" IMD image and use that to boot the CS3 via the PerSci 299 drive? If not, what are my options for downloading a bootable 8" hard-sectored CDOS disk? I am setup with ImageDisk, but haven't worked with hard-sectored 8" disks before.

    2. If I can't get the PerSci 299 to work, what are my other options - hookup a single-sided 8" drive (per the article by Martin Eberhard) hopefully to use with soft-sectored disks, or perhaps use a single-sided 5" floppy drive instead (I see that the 16FDC was intended to work with the TM100).

    3. The power supply circuitry on the rear panel has some interesting complexity to it. There's wiring that provides power (to or through a relay) that only get power when the rear-panel mains switch is in the off position. Any idea what this is for? I figured perhaps its part of a voicecoil retraction circuit, but haven't found anything to support that. John's site has a manual for the CS3, but it's for the later version that supports TM848 drives, so doesn't have any information about the power supply or drives in my CS3.

    I appreciate any help or info about the 16FDC and PerSci drives. Thanks.


    It's only the second-heaviest machine?!? You need to install a second 299!

    Your 16FDC and CDOS 2.xx should support DS/DD 5" and 8" disks as well as an IMI hard disk, but I don't think you'll be able to use hard-sector diskettes. Not every PC will be able to create a diskette from an image due to the first track being single-density FM; Dave's site has a list of which FD controllers are known to work.

    The Perscis are great when they work but notoriously unreliable; you should be able to use a 5 1/4 DS/DD drive; I think the 16FDC can also handle a 'normal' 8" drive as well as a 5 1/4 HD drive emulating an 8" one.

    Are you sure about powered circuits with the main switch off? AFAIR when the main switch is off everything is off; it powers a small 24V supply which in turn picks the relay controlling the main power supply.

    Have fun!



      My friends and I at high school in country Victoria spent a lot of time between classes packed into a storeroom playing games and writing BASIC programs on a Crememco System 3 with four floppy drives that the school had retired from school administration duties and made available to students. I will be following the progress of your restoration with interest.

      Good luck!