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Thread: 286 boards : missing bios chip(s) and memory

  1. #1

    Default 286 boards : missing bios chip(s) and memory

    Hi,

    I have 2 286 boards that I would like to verify but they came without bios chips and without memory.

    BIOS chips

    Assuming I can find a BIOS image for these boards (I read that it should be possible to find generic 286 bios chips), would I be able to use the following blank chips

    https://benl.rs-online.com/web/p/eprom/1276559/

    and program them with this programmer :

    https://benl.rs-online.com/web/p/products/9195501/

    Memory

    Some questions on the memory :

    • One board allows you to mount a SIMM socket header like this : https://benl.rs-online.com/web/p/simm-sockets/3789419
    • One board has support for SIPP modules but I don't have those. Would the header above also "fit" in these SIPP header ? (perhaps not mechanically stable)
    • On both boards I see empty 16 pin DIP and 20 pin DIP sockets. Can these also be used to add memory ?



    2019-10-11 23.20.20.jpg
    2019-10-11 23.20.57.jpg
    Retro enthousiast. Love everything < 486. Learning and sharing on my little channel

  2. #2
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    The "combo" memory layout was not uncommon in the later 80286 boards; 256K, 1M and SIPP. If you want to use SIMMs, you can use a SIMM socket inserted into the SIPP sockets--the pinout's the same. Or you can solder some pins onto a SIMM--I remember a guy who fabbed up the 256KB SIMMs and SIPPS--he used the same PCB, just added pins for the SIPPs.

    You may want to re-think using an OTP EPROM--if you screw up, the thing goes in the trash. Better to get a UVEPROM, or even an EEPROM.

  3. #3

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    Am I seeing that right? 224 Euros for a TL866A? That seems about 10 times too much.

  4. #4

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    Quote Originally Posted by jafir View Post
    Am I seeing that right? 224 Euros for a TL866A? That seems about 10 times too much.
    Way too much, Isn't there a newer model out now, The Tl866II PLUS, I don't have one so no idea what they are like.

  5. #5

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    Quote Originally Posted by Malc View Post
    Way too much, Isn't there a newer model out now, The Tl866II PLUS, I don't have one so no idea what they are like.
    You can get the Tl866II PLUS for about 60-70 EUR from China. Don’t think the big parts suppliers in Europe sell them for those prices.
    Retro enthousiast. Love everything < 486. Learning and sharing on my little channel

  6. #6

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    Quote Originally Posted by jafir View Post
    Am I seeing that right? 224 Euros for a TL866A? That seems about 10 times too much.
    10 times might be pushing it ... but yeah 3 to 4 times more expensive compared to those chinese shops.
    Retro enthousiast. Love everything < 486. Learning and sharing on my little channel

  7. #7

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    Quote Originally Posted by Chuck(G) View Post
    The "combo" memory layout was not uncommon in the later 80286 boards; 256K, 1M and SIPP. If you want to use SIMMs, you can use a SIMM socket inserted into the SIPP sockets--the pinout's the same. Or you can solder some pins onto a SIMM--I remember a guy who fabbed up the 256KB SIMMs and SIPPS--he used the same PCB, just added pins for the SIPPs.

    You may want to re-think using an OTP EPROM--if you screw up, the thing goes in the trash. Better to get a UVEPROM, or even an EEPROM.
    Will try those simm adapters. Do you know what kind of ram chips could go in those dip sockets ?
    Was searching for those uv eproms but few shops were selling them. And also 3x the price as those otp’s.

    And what are the chances of me finding a bios rom for those boards ?
    Or would a generic 286 bios rom work just as well ?
    Retro enthousiast. Love everything < 486. Learning and sharing on my little channel

  8. #8
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    256KB (parity) were usual for these on 286 boards.

    The 16-pin sockets would probably take 41256 or equivalent.
    The 20-pin sockets would likely be 1Mx1 (e.g. Toshiba 511000, or NEC D421000 or the like (there were many manufacturers; I think I used Hyundai).

    A generic BIOS would definitely be worth a try. MZD has a few candidates.

    Try an EEPROM, such as 28C256--they're still available. (e.g. Jameco wants about $6 the each). At least that way, if you foul up, you get to try again without generating more e-waste.

  9. #9

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    You are probably already aware that those boards have two EPROM sockets in which the BIOS will be divided, usually by even/odd bytes. Yes, many early model 286 BIOS's will work with other early boards but have seen issues with later models... especially ones with a single BIOS chip. I would suggest trying to find BIOS's from a boards with the same chipset and without any onboard features (video, I/O, floppy, etc.) which some 286 boards did have... it shouldn't take too much sleuthing to find one for the Texas Instruments board you have there. Of course you'll also need a keyboard bios/controller chip too, preferably matching to the bios if possible.

    If those boards were attacked by a chip pulling scrapper then I highly suggest closely inspecting them for scratches and bent pins, especially on the bottom where scratches can more easily break traces and bent pins can touch places they shouldn't. Also check for ISA slots with damaged pins inside shorting to each other (I've seen it enough times). I just got through reviving two 'dead' boards after the poor things were scrapper attacked, usually it's not too bad and usually just involves bridging broken traces, if any. A thorough visual inspection under a magnifying glass can go a long way in saving you time. Those boards will be grateful to you for getting them running again. Good luck!

  10. #10

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    Quote Originally Posted by RetroSpector78 View Post
    and program them with this programmer : ...
    I only can see you live somewhere in Belgium. Ik woon in Heerlen / je vie en Heerlen (NL) so if that is near enough, I can program the EPROMs for you. I have enough scrapped ones laying around you can have for free.
    With kind regards / met vriendelijke groet, Ruud Baltissen

    www.baltissen.org

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