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Thread: S100 hard disk controller

  1. #11

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    Yes, it was just an ISA card. The controller is simple to use.
    I tied all the address lines but one and used my own decoder for it.
    I didn't use the ROM space but on an S100, that would make sense.
    My processor had not 8 bit mode so an 8 bit EPROM was of no
    value to me.
    I found the commands and port definitions someplace on the web.
    They were reasonably easy to write driver code for. The controller
    does most of the work.
    A SASI might be more flexable but it was just a standard MFM controller.
    Dwight

  2. #12

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    A nice option to use an isa card. I didn't realize that it was an option...

    But I like to follow the way of that time... I'd love to make that HCA S100 board from the byte magazine.

    http://www.classiccmp.org/cini/pdf/b...20byte0383.pdf

    But I'm now half way drawing and I found two little errors in the schematics...
    An 7474 was marked ad an 7405, and a 7404 has to be an 7405.
    That 7474 was too obvious, but that 7404/5 was a bit nasty... The difference is the open
    collector of the 7405. The scans of the color pictures seem to confirm my conclusion.

    So I'm a bit worried about other possible errors which I didn't see...

    Was there an option to order these PCB's back then? And does anyone know
    if there were PCB drawings available?

    Regards, Roland
    Wanted: case for Altair 8800 in good or bad shape or even a replica.

  3. #13
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    If you're just wanting a hard disk interface, John Monahan/s100computers.com has an IDE board for S-100. It uses an Intel 8255 PIA to talk to the IDE device, so there's no issue with 8 vs 16 bit compatibility.

    Of course, there's nothing wrong with hacking an old interface onto the S-100 bus, just because you want to

  4. #14

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    Quote Originally Posted by glitch View Post
    If you're just wanting a hard disk interface, John Monahan/s100computers.com has an IDE board for S-100. It uses an Intel 8255 PIA to talk to the IDE device, so there's no issue with 8 vs 16 bit compatibility. Of course, there's nothing wrong with hacking an old interface onto the S-100 bus, just because you want to
    I know I've got Johns kicad drawings because the S100 outline is in it. I've never made a PCB using Kicad.
    Normally I use Altium. But because kicad is free I can share the drawings with any other hobbyist.
    Really, I don't know if anyone likes it or not... But there are a lot SASI-MFM interfaces out there...

    So this board gives me the opportunity to use authentic hardware... If it will ever be a success...
    You know, time, other projects... But I'm working on it now... Just fun. I guess wire wrapping is just
    as much work as drawing the pcb. So why not

    In the meanwhile I see more hardware errors... On the PCB there are four resistor arrays.

    resistor arrays.jpg

    But not in the schematics...

    schema 2.jpg / schema 1.jpg / schema 3.jpg

    Yes I can think of where they should be in the schematics. Two of them
    will probably be the pull-ups for the address switches..
    But there are too many directly visible errors in the document.
    So how many invisible errors are there in the document?

    I guess I'd better quit this project full of errors... Thanks Byte...

    Regards, Roland
    Last edited by Roland Huisman; May 25th, 2017 at 01:58 PM.
    Wanted: case for Altair 8800 in good or bad shape or even a replica.

  5. #15
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    Hi
    The resistor packs are near the components they support. The switches need pull ups so that when they are closed they are low (ground) but when they are open they are high (VCC). Also the pins going to the interface are likely to have pull up resistors. The 74LS38 is open collector so it will likely also have pull up resistors.

    Just zoom in on the photo to get clues. Not marking pull up resistors is not really an error and was/is common practice in making schematics. Sometimes they are annotated as asterisks or other symbols or the designer is just expected to know to add them.

    Good luck, Andrew Lynch

  6. #16

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    Quote Originally Posted by lynchaj View Post
    The resistor packs are near the components they support. The switches need pull ups so that when they are closed they are low (ground) but when they are open they are high (VCC). Also the pins going to the interface are likely to have pull up resistors. The 74LS38 is open collector so it will likely also have pull up resistors.
    Hi Andrew. Yes, that is the way to check where these pull-ups need to be. No rocket science...

    Quote Originally Posted by lynchaj View Post
    Just zoom in on the photo to get clues.
    Yes, that was exactly what I was doing Just double checking...

    Quote Originally Posted by lynchaj View Post
    Not marking pull up resistors is not really an error and was/is common practice in making schematics.
    Sorry, here I disagree a bit... In my opinion it is really an error because Byte made an article for people to make their own pcb.
    A lot of people are not that familiar with designing/building hardware. Besides that, with leaving out those resistors, you are also
    leaving out the values of them... Datalines will need a lower Ohmic value then the switches do. But in my opinion you can not
    expect from a Byte magazine reader to just know that he should put in pull-ups without even mentioning them in the text.

    So by checking the schematics for the pull-ups I found even more errors.
    Inputs connected only to inputs (ia0 and ia1), pin numbering errors in components...
    Pin labels which can't be found in the other schematics...

    I think it is useless to go any further with this project. A waste of time...
    It is just very bad documented and there will probably be a lot more errors!

    I was wondering if Byte also made correction articles for their projects.


    Any other suggestions for a project using old hardware? Or is it better to
    just pay $$$ dollar to get a hard disk on a S100 system...?

    Regards, Roland
    Last edited by Roland Huisman; May 26th, 2017 at 02:18 AM.
    Wanted: case for Altair 8800 in good or bad shape or even a replica.

  7. #17
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    Quote Originally Posted by smp View Post
    I think that Kipp Yeakel ( a member here ) may have experimented with that configuration. Maybe he'll speak up about his experience?

    smp
    While I do have the drive, controller, and some documents, it is still on the todo list and pretty far down that list as well. Since moving to another state, my electronics shop has not been put back together. Sorry for the lack of help..
    Kipp
    Looking for: Altair 8800, Ithaca Intersystems boards, software, manuals. and Jade bus probe card.

  8. #18
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    Hi
    If there is significant uncertainty about the schematic it might make sense to build a prototype with wire-wrap first to confirm the design. Then once you know it works commit the design to a PCB.

  9. #19
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    Quote Originally Posted by Roland Huisman View Post

    Sorry, here I disagree a bit... In my opinion it is really an error because Byte made an article for people to make their own pcb.
    A lot of people are not that familiar with designing/building hardware. Besides that, with leaving out those resistors, you are also
    leaving out the values of them... Datalines will need a lower Ohmic value then the switches do. But in my opinion you can not
    expect from a Byte magazine reader to just know that he should put in pull-ups without even mentioning them in the text.

    So by checking the schematics for the pull-ups I found even more errors.
    Inputs connected only to inputs (ia0 and ia1), pin numbering errors in components...
    Pin labels which can't be found in the other schematics...

    I think it is useless to go any further with this project. A waste of time...
    It is just very bad documented and there will probably be a lot more errors!

    I was wondering if Byte also made correction articles for their projects.


    Any other suggestions for a project using old hardware? Or is it better to
    just pay $$$ dollar to get a hard disk on a S100 system...?

    Regards, Roland
    Yes, I agree. That seems unusual for Byte articles to have so many errors. I thought they were better than that. What a shame. I wonder if the project has been taken up elsewhere and updated. Seems like there would be someone at S100computers.com who would be interested in working on a project like that just for the historical purposes.

    Good Luck, Andrew Lynch

  10. #20

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    Quote Originally Posted by lynchaj View Post
    If there is significant uncertainty about the schematic it might make sense to build a prototype with wire-wrap first to confirm the design. Then once you know it works commit the design to a PCB.
    Yes, I think that is the best way to go. Somehow I can't get my head off this design.
    I've ordered this breakout board http://uxpro.com/shop/index.php?rout...&product_id=72
    So I can experiment without using an original S100 experiment board...

    Quote Originally Posted by lynchaj View Post
    I wonder if the project has been taken up elsewhere and updated.
    I hope so! If anyone built it please give me an update

    Quote Originally Posted by lynchaj View Post
    Seems like there would be someone at S100computers.com who would be interested in working on a project like that just for the historical purposes.Good Luck, Andrew Lynch
    Yes, for me it's also the historical part which I like. It is an original design from the end of the S100 time.
    I've studied the Xebec S1410 datasheet which gave also some more info. We will see where it ends...

    Regards, Roland
    Wanted: case for Altair 8800 in good or bad shape or even a replica.

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