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RetroHacker_
July 14th, 2009, 04:36 AM
While sorting through the junk in the basement, I came across an old Dell motherboard with an Intel DX4 processor upgrade on it. For reference, the Intel DX4 is a triple-clocked 486. It lives on a little adapter board with a voltage regulator on it, since it runs at 3.3v and not the 5v of the earlier 486's.

This one is 100mhz, and according the the silkscreening on the Dell motherboard, the old board was jumpered for 33mhz. Perfect! I've got a 33mhz 486 in service upstairs! I'll go plug this in.

So, after some careful chip-extraction (this 486 predates ZIF sockets...), I plugged the clock tripled DX4/adapter board combo into the socket and hit the switch.

It posts! It's alive! BIOS goes through and does it's thing, then it comes to load the OS. "Loading Linux......................................."

And then it crashes horribly. Sometimes it just prints junk to the screen, other times it just lets out a long BEEEEEEEEEEEEEP, other times it throws up a Block Move Error.

So, apparently this board is not compatible... Anyone know what the criteria is for a compatible board? I honestly don't remember a whole lot about the DX4 beyond what I've posted above.

-Ian

carlsson
July 14th, 2009, 05:15 AM
Perhaps there is a factor such as memory speed, if the CPU will write and read faster than what the memory chips can cope with? Did you try the whole Dell board?

RetroHacker_
July 14th, 2009, 06:05 AM
Memory clocking might have something to do with it, this machine does use 30 pin memory. But from what I understand, while the processor internally runs at 100mhz, it still talks to the bus at 33mhz.

No, I did not try the whole Dell board, it's one of those funny ones that requires a riser card, so I wouldn't be able to actually use it for anything. It has onboard video, so it should boot by itself, but I wouldn't be able to add any kind of expansion cards like the all-important ethernet.

-Ian

cosam
July 14th, 2009, 01:46 PM
My guess would also be some kind of timing issue. You might be able to get it working by playing with wait states.

Anonymous Coward
July 14th, 2009, 05:18 PM
You should make sure the CPU socket on your 486 board is set correctly for that chip. There are two versions of the DX4 overdrive. One is for 486SX pinout and the other for 486DX. Your 486 motherboard should allow you to configure the socket for either 486SX, 486DX or 487SX. These three chips all use similar but slightly different pin configurations. You'll have to look up the model on your DX4 chip and set the board accordingly.

wolfie
July 14th, 2009, 08:20 PM
i agree with Anonymous Coward. i built a 486 server with a dx4 and there is a huge list of other proccessors that will work with the motherboard i used but you would have to change all the jumpers.