the K6 233 TDP is almost twice of what you have right now, so it's a bad idea even if it worked at 1.5x, unless you want to fry the regulator. the heatsink on this board seems to be particularily tiny. boards went away from linear regulators for a reason when the K6 233 launched.

as for performance, you would need a K6-2 on an adapter to make a real difference, but even then it may be advisable to cool the regulator with a fan.

There is a resistor mod for getting the 3x multiplier to work on these boards, Necroware does it in one of his videos. Speaking of Necroware, one of his voltage regulators would allow you to run a K6-2 @ 400 MHz on this board. Probably not worth the effort, but if you really wanted to, you could even go as far as a K6-3+ @ 400 MHz that way. Also, the Necroware regulator (combined with the resistor mod) would allow you to use the K6 233 with no fear of having the board's linear regulator blow up.

He covers the resistor mod around the eight minute mark in this video: https://www.youtube.com/watch?v=J0NLGfocviU

TLDR: with the board Necroware is working on (a similar FX chipset board) what he encountered was the difference in how the P54 and P55 CPUs interpret the multiplier setting on the board. A 200 MHz P54 worked with no issue, but the P55 MMX CPU would only run at 166 no matter how he set the multiplier until he added a resistor.

If he's running a P200, he already has 3x multiplier working.

A K6 uses the same multiplier settings (values for BF0, 1 and 2) as Pentium MMX so 1.5x setting will run at 3.5x = 233MHz with a 66MHz bus clock. Question is whether the board can handle it.

The voltage regulator is key here. Can you look up the exact brand+model of the one on your board? (it's the IC attached to the big heatsink under the socket)

Depending on its specs, either the K6-233 will be fine or it will probably cause the board to go up in flames.

As for performance, the question is: in what?

K6 and P54C (Pentium 200) have very different strengths. K6 has a faster ALU clock-for-clock, giving about 5% faster performance in Doom at the same speed. So for ALU-intensive tasks, the K6-233 would be about 22% faster than the P200. However the Intel FPU is a lot more powerful, about 30% faster clock-for-clock, so in Quake the K6-233 would perform about 11% worse than the P200. Now, most period-correct software is ALU-intensive, Quake is definitely the outlier here - but it really depends on what you want to do with this system.

dionb wrote on 2025-09-23, 21:11:

If he's running a P200, he already has 3x multiplier working.

A K6 uses the same multiplier settings (values for BF0, 1 and 2) as Pentium MMX so 1.5x setting will run at 3.5x = 233MHz with a 66MHz bus clock. Question is whether the board can handle it.

Depending on its specs, either the K6-233 will be fine or it will probably cause the board to go up in flames.

He already says the p233mmx runs at 166mhz.

Since he has an intel 233 you really can’t do better, when he installs it with a 1.5x multiplier he should use a diagnostic utility to validate that it really is running 233 despite the board “saying “ 166mhz.

It’s possible the boards bios doesn’t recognize anything past 166 and is erroneous

My first Windows 95 computer had a K6-233. One day the fan stopped working, and the processor overheated and died. They don't have heat protection.

So I replaced it with a similar 300 MHz CPU that dropped straight in. Then I had the Windows bug of protection error at start, due to a divide-by-zero problem. After getting replacement files, we were back in business.

Hi guys, thanks for all reply!

Ont think i was thinking you say, is that a 233mmx have 1.5x, i did not realize about this!! i only tried 2x and 3x on this CPU, what a mistake!

Sadly right now im not im home, in 2 days i will be home and tried 1.5x on the 233mmx! i preffer to use this over the K6 better tpd, the only is voltage difference. In other hand MMX 233 are very cheap and easy to find

I will tell you guys

auron wrote on 2025-09-23, 20:10:

the K6 233 TDP is almost twice of what you have right now, so it's a bad idea even if it worked at 1.5x, unless you want to fry the regulator. the heatsink on this board seems to be particularily tiny. boards went away from linear regulators for a reason when the K6 233 launched.

as for performance, you would need a K6-2 on an adapter to make a real difference, but even then it may be advisable to cool the regulator with a fan.

ok, yes, you are very right about TPD, i did not notice this

I replace the regulator on this board and add a big heatsink because when i bought was already dead, but still i dont trust much to install the K6 after realize the new tpd, thanks for this

dionb wrote on 2025-09-23, 21:11:

As for performance, the question is: in what?

Oh i believe here in vogons you people have a crystal ball !! sorry, you right

Im not a big gammer, i mostly use retro computer for software, and i love console emulators. For games, the top I play is Doom, then even a top end 486 is enought for me, but like to have some extra power for callus emulator for example, that have little slowdown in pentium 200, and i read in readme can benefit of mmx instructions and large l1 cache

rmay635703 wrote on 2025-09-24, 00:42:

[...]

Since he has an intel 233 you really can’t do better, when he installs it he should use a diagnostic utility to validate that it really is running 233 despite the board “saying “ 166mhz.

Possible.

However a K6 is faster clock-for-clock than a P55C in ALU, so if the code is ALU-heavy it might still be faster.

theelf wrote on 2025-09-24, 08:00:

[...]

ok, yes, you are very right about TPD, i did not notice this

I replace the regulator on this board and add a big heatsink because when i bought was already dead, but still i dont trust much to install the K6 after realize the new tpd, thanks for this

What you can or can't trust depends on the specs of the regulator. Which type did you use?

Oh i believe here in vogons you people have a crystal ball !! sorry, you right

Im not a big gammer, i mostly use retro computer for software, and i love console emulators. For games, the top I play is Doom, then even a top end 486 is enought for me, but like to have some extra power for callus emulator for example, that have little slowdown in pentium 200, and i read in readme can benefit of mmx instructions and large l1 cache

In Doom, the K6 would definitely be faster. As for the emulator, no idea. You'd have to benchmark that yourself. If software does actually use MMX extensions, their presence will usually make a big difference. There aren't many MMX benchmarks, but THG looked at K6 MMX performance and found it to outperform P55C MMX in some cases even using Intel's own benchmark. In any event it's in a similar ballpark. So K6 vs P55C again comes down to whether the code leans on ALU or FPU - but if MMX is at all relevant, either will obviously thrash the P54C which doesn't have it.

If your concern is performance then it's best to just go straight to a Pentium II motherboard + CPU and leave this one for what it's good at. Unless you also happen to have some kind of 430TX or VX or Super Socket 7 motherboard already, which would be better suited to the types of CPUs you've mentioned, but I'm guessing you don't.

forget to answer to rmay635703, yes the 166mhz are real, tested with benchmark tools and a doom timedemo

dionb wrote on 2025-09-24, 08:24:

Possible. […]
Show full quote

rmay635703 wrote on 2025-09-24, 00:42:

[...]

Since he has an intel 233 you really can’t do better, when he installs it he should use a diagnostic utility to validate that it really is running 233 despite the board “saying “ 166mhz.

Possible.

However a K6 is faster clock-for-clock than a P55C in ALU, so if the code is ALU-heavy it might still be faster.

theelf wrote on 2025-09-24, 08:00:

[...]

ok, yes, you are very right about TPD, i did not notice this

I replace the regulator on this board and add a big heatsink because when i bought was already dead, but still i dont trust much to install the K6 after realize the new tpd, thanks for this

What you can or can't trust depends on the specs of the regulator. Which type did you use?

Oh i believe here in vogons you people have a crystal ball !! sorry, you right

Im not a big gammer, i mostly use retro computer for software, and i love console emulators. For games, the top I play is Doom, then even a top end 486 is enought for me, but like to have some extra power for callus emulator for example, that have little slowdown in pentium 200, and i read in readme can benefit of mmx instructions and large l1 cache

In Doom, the K6 would definitely be faster. As for the emulator, no idea. You'd have to benchmark that yourself. If software does actually use MMX extensions, their presence will usually make a big difference. There aren't many MMX benchmarks, but THG looked at K6 MMX performance and found it to outperform P55C MMX in some cases even using Intel's own benchmark. In any event it's in a similar ballpark. So K6 vs P55C again comes down to whether the code leans on ALU or FPU - but if MMX is at all relevant, either will obviously thrash the P54C which doesn't have it.

In callus emulator, you have or fpucopy or mmxcopy to speed up things, but no idea how much mmx can help here, i tried a newer SS7 board, tested both 200 ad mmx200, and really i did not see much or any dfference from mmx to fpu copy, but yes i found better the MMX cpu because L1, maybe 10% more fps in emulator

devius wrote on 2025-09-24, 09:05:

If your concern is performance then it's best to just go straight to a Pentium II motherboard + CPU and leave this one for what it's good at. Unless you also happen to have some kind of 430TX or VX or Super Socket 7 motherboard already, which would be better suited to the types of CPUs you've mentioned, but I'm guessing you don't.

Changing motherboard is out of question, love this one, have solid mrbios support and 5 ISA, is amazing

I have more than 200 motherboards, from XT to pentium 3, maybe 30-40 different boards from socket 5 to slot 370, no problem to pick any, but with 5 isa and mrbios support, only this one

About regulator, not remember, but was exactly same as original, it was dead, but still can read the type

Repo Man11 wrote on 2025-09-23, 20:50:

There is a resistor mod for getting the 3x multiplier to work on these boards, Necroware does it in one of his videos. Speaking of Necroware, one of his voltage regulators would allow you to run a K6-2 @ 400 MHz on this board. Probably not worth the effort, but if you really wanted to, you could even go as far as a K6-3+ @ 400 MHz that way. Also, the Necroware regulator (combined with the resistor mod) would allow you to use the K6 233 with no fear of having the board's linear regulator blow up.

He covers the resistor mod around the eight minute mark in this video: https://www.youtube.com/watch?v=J0NLGfocviU

TLDR: with the board Necroware is working on (a similar FX chipset board) what he encountered was the difference in how the P54 and P55 CPUs interpret the multiplier setting on the board. A 200 MHz P54 worked with no issue, but the P55 MMX CPU would only run at 166 no matter how he set the multiplier until he added a resistor.

I will check the video when home, thanks