First post, by computerguy08
I had a bit of free time recently and decided I want to do some experiments with my UMC Pentium board which I got recently, a Gigabyte GA-586AM.
On the PCB I noticed what looked like footprints for a possible VRM upgrade, which would've given the board dual voltage rails for a Pentium MMX presumably.
So I did the right thing, desoldered the bypass wire from the Vcc2 rail (Vcore) and added my own DC-DC step down converter instead, which I set conveniently at cca. 2.2V
There was one more challenge though: the K6-2 wouldn't fit in the socket, one corner was floating. Upon further investigation, I learned K6-2's only fit in Socket 7 because there is one extra pin in one of the corners.
Checking the datasheet reveals that pin is used just for keying, which is normally a good thing, you wouldn't want to send 3.5V on the core, it would probably fry it 😜
For the conditions of my experiment, it was safe to remove the pin from the CPU, I had set up an appropriate VRM.
And after a power switch flip, it came to life!
Because the BIOS is so old on this board, there was no chance it would have K6 microcodes, therefore it was detected as a 486DX-66, which is funny.
After a bit of playing around, I was able to get the K6 running at 300MHz (50FSB x 6), anything faster wouldn't POST.
Still, the results are pretty impressive for a Socket 5 board.
Moral of the story: you can run a K6-2 on Socket 5, but make sure the board has separate power rails (you can check with a multimeter).