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Thread: DIY 286 to 386 upgrade?

  1. #1
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    Default DIY 286 to 386 upgrade?

    Now I know this might be a bit "out there", But I do know there were companies involved in making 286 to 386/486 upgrades. But those are almost unobtanium and go for substantial prices when they do come about.

    So... Does anyone happen to have schematics, or know of whats involved in processor retrofits? Just curious.

  2. #2

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    I had one which was a PC-on a card that plugged into an ISA slot. It was no stellar performer by any means. I may actually still have one somewhere.

  3. #3
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    While I don't have a schematic, I do have an image here of a Kingston upgrade. Not sure what the Austek chip is thanks to the label but all Kingston 286 -> 386 upgrades have it.

    http://i.imgur.com/zWl4HfR.jpg

  4. #4

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    The Austek chip is a cache controller. The cache is what really makes the upgrade go faster than the original 286.

  5. #5
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    Unfortunately that doesn't really help my situation.

    The card is loaded with PAl chips which.... well there a mystery.

    I was hoping someone had a magazine article or a application note or something from years past that explains how to adopt a 386 into a 286 bus.

    Everything between the two is the same except for the state control lines on the output. These control lines are used to signal bus conditions such as a protected memory read IO read etc....

  6. #6
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    Quote Originally Posted by nestor View Post
    The Austek chip is a cache controller. The cache is what really makes the upgrade go faster than the original 286.
    To be fair, 32-bit wide access and zero wait is what makes it go faster and why most upgrade options had local RAM. You can achieve that with modern 10-15ns SRAMs without cache control.
    "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

  7. #7

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    Zenith used to have a 486 upgrade board for the Z-248 series 286 machines. The 248 was very similar to how an S-100 board was set up, and the upgrade replaced all the discrete cards with all in one full length card with the CPU, I/O, FDD & HDD controllers, memory, and video (if I recall correctly) onboard.

  8. #8
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    Why? If you want to experience 386 or 486 computing buy a 386 or 486. they are still plentiful and cheap...
    Dave
    G4UGM

    Looking for Analog Computers, Drum Plotters, and Graphics Terminals

  9. #9
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    Quote Originally Posted by g4ugm View Post
    Why? If you want to experience 386 or 486 computing buy a 386 or 486. they are still plentiful and cheap...
    +1

    I don't quite get trying to upgrade a vintage system to a completely different level. Why even collect the vintage system the first place if that is what you want to do?

    I bought an XT/286 because I wanted an 80286 machine.
    I bought a Deskpro 486/33M because I wanted an 80486 EISA machine (although it does have a 66Mhz CPU card in it now but that was an original option).
    It would make zero sense to me to try to upgrade the XT/286 to a 386 or 486 level instead of just using the 486/33M.

  10. #10
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    We have had a couple of threads like this where folks want to upgrade 386sx to 486 or 286 to 486 with after market upgrades.

    From what I remember those were all expensive in the day, for what you got. Often they didn't work that well as the CPU often is not the only bottle neck, and you still ended up with a slow disk and slow RAM or a 32-bit CPU bodged onto a 16 bit bus. They must be like hens teeth these days and I wouldn't want to spoil a nice original 286...
    Dave
    G4UGM

    Looking for Analog Computers, Drum Plotters, and Graphics Terminals

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