The only manual I found doesn't seem to line up as far as the diagram on my board is concerned (Rev. B2.) The voltage dip switches are 1-4 in the manual and 1-5 on my board. It came det up for a K6-2 500 and when I put the K6-III 550 in it, it came up as a K6-III 500. I started playing with the CPU dip switches and managed to get it to 550Mhz. However, all other settings make it below 500. I tried adjusting the voltage dip switches and either nothing changes, or it doesn't post. I am worried about damaging the board/CPU, though I am trying to get to 600Mhz. I am reading that 600 may be max on this board, or slightly above but perhaps with stability issues.

Many MVP3 (most?) motherboards only go up to 100 MHz frontside bus, and if this is true of the one you have, 600 MHz will be the highest speed you can achieve. To get the six multiplier you have to set the motherboard to 2x. The CPU uses 2x as 6x and 6x100 = 600 MHz. This can sometimes be achieved at the default core voltage setting of the CPU, and if you do have to overvolt it, it will usually be stable at 2.1 or 2.2 core voltage. I've run K6-+ CPUs at 2.4 for extended periods, but that's higher than recommended and it was only to try and get the highest possible overclock. That sort of thing leads to a lot of work to get a tiny bit better performance, so you may well be better off if you are limited to 600 MHz.

Some MVP3 motherboards have undocumented FSB settings, so you may want to do some searching on your particular motherboard.

If your board can go above 100 MHz FSB, you generally want to have the highest frontside bus speed you can achieve while lowering the multiplier. But you can quickly run into an issue with the motherboard's cache. The cache chip on the motherboard does help performance some as level 3 cache, but those memory chips often don't work when the FSB gets too high. The best Super 7 board I have will do 5.5x112=624. I've had it running at a higher FSB with a lower multiplier, but I had to disable the motherboard's cache to do it so the net performance increase was nothing. Faster FSB speeds help with memory bandwidth and that's especially helpful as the MVP3's memory bandwidth wasn't great. But if you play the right sort of games, none of this will really be an issue.

Repo Man11 wrote on 2024-04-23, 22:51:

Many MVP3 (most?) motherboards only go up to 100 MHz frontside bus, and if this is true of the one you have, 600 MHz will be the highest speed you can achieve. To get the six multiplier you have to set the motherboard to 2x. The CPU uses 2x as 6x and 6x100 = 600 MHz. This can sometimes be achieved at the default core voltage setting of the CPU, and if you do have to overvolt it, it will usually be stable at 2.1 or 2.2 core voltage. I've run K6-+ CPUs at 2.4 for extended periods, but that's higher than recommended and it was only to try and get the highest possible overclock. That sort of thing leads to a lot of work to get a tiny bit better performance, so you may well be better off if you are limited to 600 MHz.

Some MVP3 motherboards have undocumented FSB settings, so you may want to do some searching on your particular motherboard.

Thank you for this information! Unfortunately, I am having a difficult time finding information on this motherboard. I found another thread with the same board and the poster said that the CPU ran at 600. There was a pic of the board and I tried setting the switches to what I saw in the pic, but to no avail. Every combination of switches I am trying nets me 550 tops, else it goes lower (208Mhz so far) or doesn't post. Despite my years of PC experience, I am a total neophyte with this sort of thing. If I can get it to 600, I'll probably be happy with that, unless a bit more is somehow possible on this particular set up.

Another thing I am noticing is that if I have the dip switch combination set to 550 (DP1 setting don't seem to change that or it doesn't post,) my CPU fan header works. If I change the switches, it stops working. I am going to keep hunting for info as I am hoping to make this system my main retro machine and thus need to know all that I can discover about it.

It's possible that there are speed settings where the POST screen won't be able to show the correct speed as it wasn't included in the BIOS code. If the multiplier is set at 2x and the FSB is set to 100 MHz then you will have 600 MHz regardless of what the POST screen displays. You can check it with DOS programs such as Speedsys or in Windows with CPU-Z if the POST screen is incorrect.

Repo Man11 wrote on 2024-04-23, 23:46:

It's possible that there are speed settings where the POST screen won't be able to show the correct speed as it wasn't included in the BIOS code. If the multiplier is set at 2x and the FSB is set to 100 MHz then you will have 600 MHz regardless of what the POST screen displays. You can check it with DOS programs such as Speedsys or in Windows with CPU-Z if the POST screen is incorrect.

I found the revision B manual, and my system is now booting as a K6-III 600!

I think that 600 is indeed the max, unless I am doing something wrong. I kept upping voltage, and it remained the same even when checking with speedsys. After a point, it doesn't post.

I have been letting it sit idle with the temporary fan. At 500Mhz it was 31C/87F idle, and it remains so despite running 100Mhz faster.