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replacement for 80286

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    replacement for 80286

    Ok, 2 questions....... I have an IBM AT 5170 Gen 1 (256/512 motherboard) with a 6MHz 80286. Can I just pop out the CPU and drop in a faster one ? Is so, what do you find to be the best CPU to replace it with ? The BIOS has been upgraded to the Gen 3 July 10, 1985 BIOS chips. Thanks !

    #2
    the short answer is 'no'

    IBM did make a 8MHz AT, so you might be able to convert it but IIRC there is some kind of BIOS check that prevents over clocking

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      #3
      I believe the last batch of 5170s even had the 10MHz processor, but I was wondering if anyone had made the upgrade.

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        #4
        There were kits with the higher clock oscillator and updated BIOS to go along with the new CPU. Note that the 10 MHz AT variant from IBM was a bit unreliable so pushing that far might be unwise. It wasn't 5170 but I think was the industrial system.

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          #5
          I was in the same boat and wanted some more performance from one of my IBM AT's. Checkout my thread: HERE Where I'm going into my way of upgrading the machine. the First thing I thought of was an Intel Inboard AT, which was specifically designed to upgrade the AT to a 386. But they are very rare and expensive. Second option would have been something like a "make it 386" or Kingston "SLC NOW!" but these options again are very rare and expensive, and may have problems with the 5170 Bios or motherboard if they aren't specifically compatible.

          My IBM 5170 in question was a 6mhz version 1 board that had an aftermarket AMI bios when i got it. So the fact that now it boots up with a phoenix bios message doesn't bother me too much. and I have to admit for about $100, it was an awesome bang for the buck upgrade.

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            #6
            Originally posted by krebizfan View Post
            There were kits with the higher clock oscillator and updated BIOS to go along with the new CPU. Note that the 10 MHz AT variant from IBM was a bit unreliable so pushing that far might be unwise. It wasn't 5170 but I think was the industrial system.
            I mean the PS/2 Model 30 286 in "sort of" an AT 10mhz... all be it with the stupid proprietary crap that comes with it being a PS/2.

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              #7
              Originally posted by pinkdonut666 View Post
              I mean the PS/2 Model 30 286 in "sort of" an AT 10mhz... all be it with the stupid proprietary crap that comes with it being a PS/2.
              Well, to be frank, the Model 30 isn't much of a PS/2 either...
              Reach me: vcfblackhole _at_ protonmail dot com.

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                #8
                This is not a machine I'm keeping, but to sell. I have 2 I'm keeping, an orignal Model 339 (Gen 3 8MHz) and a wolf in sheep's clothing, a 486 motherboard in an AT case, full ISA and lots of memory. I would think a simple upgrade to 8MHz wouldn't cause too much pain, but the performance gain might not be worth it. Thanks for you thoughts.

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                  #9
                  The model 30/286 had a few 8 bit isa slots and no mc slots, no?

                  I had 1 for a while. It looked like a ps2 to me (or PoS v.2.0 . I kind of liked the whole battleship bone color scheme. More cheery then the multinational corporate beige scheme. A twist of artsy fartsy. Even after my 30 got wet and spit sparks at me, it still worked. Built real well it seemed. But weird interleaved memory arrangement. Something screwy.

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                    #10
                    Originally posted by tipc View Post
                    The model 30/286 had a few 8 bit isa slots and no mc slots, no?

                    I had 1 for a while. It looked like a ps2 to me (or PoS v.2.0 . I kind of liked the whole battleship bone color scheme. More cheery then the multinational corporate beige scheme. A twist of artsy fartsy. Even after my 30 got wet and spit sparks at me, it still worked. Built real well it seemed. But weird interleaved memory arrangement. Something screwy.
                    3 16 bit ISA slots and the world's slowest hard drive. Nice turbo AT clone except for the hard drive.

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                      #11
                      Same h/d as the model 25? Which was designated ide but wasn't "real" ide, as in 16 bit ide. Invented by Compaq if I'm not mistaken.

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                        #12
                        I acquired a 1rst gen 5170 motherboard (512K stacked chips/6 MHz) that worked fine, but I didn't have a 5170 case to put it in. Later I got my hands on a whole 5170, but it's motherboard was damaged by battery leakage, and I could never quite get it working right. This system had the next gen motherboard with the 8 MHz CPU. The crystal is socketed on these boards so I pulled the 8 MHz CPU and crystal out of the damaged board and installed them on the 1rst gen board, then I built up the system around that. I've read that some of the support chips on the 1rst gen motherboard can sometimes be unreliable past 6MHz, but this one works flawlessly at 8MHz.

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                          #13
                          Has anybody ever tried to replace a 80286 with an 80386-SX?
                          With kind regards / met vriendelijke groet, Ruud Baltissen

                          www.baltissen.org

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                            #14
                            Originally posted by Ruud View Post
                            Has anybody ever tried to replace a 80286 with an 80386-SX?
                            Is that even a thing? Even though they both use a 16-bit bus I would assume that there are enough differences that you just can't pop in a 386SX and have it work. There are the likely differences in pin out, communications with the bus and BIOS support to name a few off the top of my head.

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                              #15
                              They sold 286-386sx upgrade boards that plugged into the CPU socket and basically had no glue on them so, yes, the 386sx is directly compatible from an electrical standpoint. (And while there are minor BIOS issues they can be worked around with drivers.) The main problem is Intel never released the SX in a physically compatible form factor; it *only* came in a surface mount flat pack, so you need an adapter board to put it in a 286 socket. To make it harder 286s actually came in several socket types, so you need a board that fits your particular motherboard.
                              My Retro-computing YouTube Channel (updates... eventually?): Paleozoic PCs Also: Blogspot

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