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Thread: ISA Multi-IO Board - Preferred Connectors

  1. #1
    Join Date
    Jul 2010
    Location
    Silicon Forest, Oregon, USA
    Posts
    675

    Default ISA Multi-IO Board - Preferred Connectors

    Hi,

    I am working on an ISA 8-bit (PC/XT compatible) Multi I/O board with the following features:
    1. Floppy disk controller
    2. Compact Flash interface
    3. Two serial ports
    4. One parallel port
    5. BIOS extension / boot ROM (Flash ROM will be used)

    Obviously there is not enough space on the back of the card / ISA bracket for all the I/Os on the board. And so I am wondering what do you think is the most useful combination:
    a. One serial DE9 connector and one parallel DB25 connector on the back of the card and a 2x5 header for the second serial port. (The usual combination for such cards)
    b. Two serial DE9 connectors on the back of the card, and a 2x13 header for the parallel port. (Who uses parallel port anyway?!)
    c. CF slot on the back, headers for I/O ports (My least favorite option as I rarely replace CF cards. Also in this case a custom bracket will need to be manufactured).

    Thanks,
    Sergey

  2. #2
    Join Date
    Mar 2011
    Location
    Atlanta, GA, USA
    Posts
    1,282

    Default

    Quote Originally Posted by sergey View Post
    (Who uses parallel port anyway?!)
    Who uses an XT class machine? What will I plug my LQ-2550 into?

    I see some appeal in this. Even if an XT-IDE had a FDC, you are forfeiting the usable area on the back-plate. And even though I/O cards (even 8-bit ones) are still very common/cheap, they require 2 plates of connector space. So combining uses 2 slots instead of the usual 3.

    Typically they add a game port though. Might be a nice feature especially if it had a HardMPU (like the Scott Baker's enhanced board version) to time sequence MIDI. Many sound cards have game+MIDI but usually their MPU-401 compatibility isn't great (just raw serial only).

    For connector, I would use whatever back-plate is the most available. Keystone still makes most of those combinations and are stocked in places like Digikey.

    Of course you could cheat if willing to go SMT. A Super I/O chip would handle all the I/O + FDC. An ATF1508 would carry the memory mapped JR-IDE design (360 KBytes/s on a PCJr) in a single chip. Add a couple RAM chips and flash chip for conventional fill and DOS in ROM and I might try and stuff a Benji in its g-string!
    "Good engineers keep thick authoritative books on their shelf. Not for their own reference, but to throw at people who ask stupid questions; hoping a small fragment of knowledge will osmotically transfer with each cranial impact." - Me

  3. #3

    Default

    Quote Originally Posted by sergey View Post
    1. Floppy disk controller
    2. Compact Flash interface
    3. Two serial ports
    4. One parallel port
    5. BIOS extension / boot ROM (Flash ROM will be used)
    As Eeguru remarked, I/O cards are still very common. If I may suggest:
    1. Floppy disk controller
    2. Compact Flash interface
    3. BIOS extension / boot ROM
    4. Real Time Clock

    Knowing you, the FDC will be able to handle 1.2 and 1.44 MB as well. The CF doesn't need any further comment, I think. But the RTC is a real MUST, I must say: all MIO cards for the XT have one, AFAIK. And OTOH, I have only ONE RTC-only card for a XT (which doesn't even work ) and that is a thing you will need when using the above card according your specifications. (unless you use it in combination with your Xi808
    IMHO there are enough AT MIO cards around that can handle the COM, LPT and GAME part, so don't bother with these, I would say.

    If you add RTC, I am definitely interested so, please, keep us informed!
    With kind regards / met vriendelijke groet, Ruud Baltissen

    www.baltissen.org

  4. #4
    Join Date
    Jul 2010
    Location
    Silicon Forest, Oregon, USA
    Posts
    675

    Default

    Alright, I'll see if I can add an RTC there.
    I am not quite sure about adding extra SRAM though. I don't want to make a monster of a card.
    ... and yes, I am going to cheat and use SMT components

  5. #5

    Default

    My Tandy 1000rlx only has one 8 bit ISA slot
    A 16 bit IDE, Ethernet, ram and sound blaster combo card would be nice :0

    Lol, nothing like being unrealistic

  6. #6
    Join Date
    Apr 2009
    Location
    scandinavia
    Posts
    234

    Default

    hello
    on my old xt-clone i had a reset button. And kind of missing it on the IBM5150.
    when you are dong alot of tests , it is a shame to have to power off power on a lot of times.

    /cimonvg

  7. #7

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    The problem is that you cannot reset a PC from a card towards the motherboard. The RESET signal on the ISA bus is motherboard towards ISA slot only. The only thing you can do is to hack the circuit on the board. I have done that but have to look again how I did it.
    With kind regards / met vriendelijke groet, Ruud Baltissen

    www.baltissen.org

  8. #8

    Default

    If that card is supposed to be "I/O", then the choice of directly-attached ports is obvious: LPT and 9-pin COM.
    Not many people will need a second COM, so let it be via an additional bracket.
    And not many people will need externally accessible CF, so again - additional bracket.

    RTC... it needs a battery, and batteries are the ultimate evil :P
    It's 2018, everything is connected to the net, and it's so easy to set the clock via net.
    But if people insist, then OK, just make sure the battery is of the rarely-leaking kind, and easily removable.

  9. #9

    Default

    Quote Originally Posted by rmay635703 View Post
    My Tandy 1000rlx only has one 8 bit ISA slot
    A 16 bit IDE, Ethernet, ram and sound blaster combo card would be nice :0

    Lol, nothing like being unrealistic
    Only reason why I didn’t put an Ethernet connector on my multipurpose card - not enough space. It very easy to remove any of existing connectors and put Ethernet instead...

  10. #10
    Join Date
    Jul 2010
    Location
    Silicon Forest, Oregon, USA
    Posts
    675

    Default

    CR2032 batteries are not particularly evil - they don't leak and easily removable and replaceable... And then there is an option to use super caps. Although I think they will not keep RTC running for a very long time

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