Putting a 486dx in an Intel overdrive slot

Arbystpossum · Sep 30, 2025

The Idea is simple enough, I have a board with an on-board 486SX-25 and I want to make it a DX2-66. It has an older blue Overdrive Ready socket as well, I tried dropping a DX2 cpu in the socket and the system won't boot. I read that the on board cpu may need to be disabled, which there is no jumper for. Does there exist a riser or spacer or something that grounds the appropriate pin so I can use a regular socket 1(i think) cpu instead of specifically an Overdrive cpu? Picture is of the socket in question.

jdmcs · Oct 4, 2025

The motherboard likely needs to have jumper settings changed for a DX2-66 processor to work. If you post a photo of the whole motherboard, we might be able to help figure out which one it is. And if a site like The Retro Web has the motherboard listed, we might even be able to help with which jumper(s) need to be changed.

Stinkerton18 · Monday at 9:38 PM

Old timer here, the Overdrive socket (and Overdrive processors) have an extra pin. It's this extra pin (pin 169) that actually disables the onboard CPU and allows the one in the socket to take over. Without the extra pin, both CPUs are essentially active at the same time and conflicting.

It was pretty rare that you could disable a soldered/onboard CPU just with jumpers, it was nearly always controlled via the extra "CPU disable" pin. That said, there absolutely is a way to use a regular 486DX chip in an Overdrive socket. Check out this VOGONS thread: https://www.vogons.org/viewtopic.php?t=68471

If you short pin 169 to ground, that will send the "CPU Disable" signal and cause the onboard 486SX to be turned off. Look at the underside of the board socket, it'll be easier to solder a jumper wire from that pin to a ground if you can't find the documentation or a jumper to disable the 486SX onboard.

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Putting a 486dx in an Intel overdrive slot

Arbystpossum

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jdmcs

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Stinkerton18

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