What actually bothers me is that the CPUs aren't any cooler at lower voltages (finger test).

The finger test is not exactly a precision measurement and you're probably not doing a direct side-by-side comparison, so I wouldn't really rely on that. But if you're just checking it at idle, there may not be much difference... it's not like the PMMX is a hot-running chip in the first place. Even at full voltage and full load they only dissipate about 12-13W.

It gets so hot you can barely keep a finger on a cooler (its a really small cooler without a fan).

Anyways... I dig the computer up to try and do some overclocking, checked the settings and this 233MMX was set to 2.1V and ran Win98 just fine. Changed the FSB to 75MHz == 266MHz and I had to raise the voltage to 2.3V. Finally the 83MHz FSB. At 2.3V it wouldn't even post. So I raised to 2.7V. It booted to DOS, ran 3Dbench but Win98 gets Protected Memory Error. Raising voltage to its Default 2.8V fixed it and runs happily at 292MHz even though BIOS reports as 266MHz - Aida16, Aida32, Memtest, Sysinfo, 3Dbench agree its 292MHz. As I don't have any Super 7 boards this is it...for now 😉

3Dbench 1.0c results:
66x3.5 = 233MHz... 175.0
75x3.5 = 266MHz... 197.4
83x3.5 = 292MHz... 218.9

Memtest 3.2:
233MHz:
L1 Cache = 174MB/s
Memory 64MB = 144MB/s

266MHz:
L1 Cache = 197MB/s
Memory 64MB = 162MB/s

292MHz
L1 Cache = 218MB/s
Memory 64MB = 180MB/s

Hope to find some ss7 board soon.

PS:
This is the chip. It's actually missing one pin in the lower right corner - I don't know its purpose. 😕

Edit:
I used the wrong 3Dbench. Now retested with 3Dbench 1.0c @292MHz.

I also noticed that results varies with different PCI graphics cards (ATI Rage Pro 4MB is the slowest - 185.0, then S3 Virge 2MB - 205.6, Voodoo 3 3000 16MB - 206.8 and the fastest of my cards is TNT2 M64 16MB - 218.9. Almost the same is with Quake 1.06. Ati Rage Pro 4MB - 58.6, S3 Virge 2MB - 63.7, TNT2 M64 16MB 66.6 and fastest is Voodoo 3 3000 16MB - 66.8.

cy

kixs wrote:

I'm wondering if anyone has done any undervolting and what are the experiences?

Sure, it seems to help, but like you I never really made a graph using a thermal sensor.
In theory undervolting is a very effective way to reduce power consumption, thus heat dissipation:
"The power consumed by a CPU is approximately proportional to CPU frequency, and to the square of the CPU voltage" source
Unfortunately Slot-1 systems often lack easy voltage reduction. So it is only with slotket adapter cards that I can go like 0,2V below stock, often in combination with a bit of underclocking.

kixs wrote:

I've tried with 166MMX and 233MMX and they both go down to 2.0V and run stable. The 166MMX even overclocks to 208MHz at that voltage. And this gets me guessing if this is normal or the jumpers on my QDI Explorer IV board are not working correctly? 😕

2.0V that is very low!? Do you have a multi meter to get a read on the voltage?

I'm interested in undervolting because I think I don't have good enough cooling for the cpu. I'd like to do some OC with it as it seems I might have a nice sample.

I don't have a multimeter. But I'm thinking on getting one - to salvage a 386DX board that had a battery leakage - now the cache doesn't work 🙁

I think running a pentium mmx overclocked,even if undervolted,only with a small cooler and no fan,it's dangerous,especially if u say the cooler gets very hot,try and get a fan.

I agree. So I took a 12cm fan, cranked it up to about 2700RPM and mounted it over the cpu for the purpose of this testing 😉

hello guyz, i would like to know how much voltage your p55c needs to run stable at 300. i increased to 3.0v and its NOT fully stable, 3dmark crashes for some times, superpi managed to finish though, and even the infamous linx(linpack based) passed.

My motherboard supports max FSB 83MHz so I can get it up to 292MHz at 2.8V - but this isn't fully tested, just for the benchmarks. From what I read so far, it usually needs around 3.4V to ran at that speed - but this is different from CPU to CPU, some are better some are worse.

I got a new ss7 board - Gigabyte GA-5AX and have done some more testing. I also got a new cooler - some hefty cooper one. For testing I don't use any paste and even don't clip it on the cpu. The cpu stays only slightly warm to the touch the second I turn off the power supply and remove the cooler - even at the highest overclock.

My cpu goes up to 330MHz (110x3) @ 3.4V but it's only 3Dbench stable. With Quake it crashes almost immediately. But its fully stable at 315MHz (105x3) @ 3.1V. Here are some benchmarks:

Test setup:
Pentium-MMX 233MHz @ 315MHz (105x3) @ 3.1V
Gigabyte GA-5AX rev 4.1
1x256MB SDRAM CAS2
ATI Rage 128 32MB

Quake (demo1): 76.4
3Dbench 1.0c : 268

For comparison:
AMD K6-3 450MHz (100x4.5)
Quake (demo1): 87.2
3Dbench 1.0c : 409.2

I've done even more testing with 3x100MHz but with different graphics cards.

Graphic card:____________Quake_______3Dbench_________Win 3.11 - Winbench 3.11 @ VGA16 mode
ISA CL-5429 2MB_________29.2_________51.6____________5.210.401
PCI ATI Rage Pro 4MB_____63.6_________195.6___________16.421.745
PCI TNT-M64 16MB_______72.5_________255.1___________17.572.386
AGP ATI Rage 128 32MB___73.0_________255.8___________19.301.540

kixs wrote on 2013-09-01, 00:02:

I'm wondering if anyone has done any undervolting and what are the experiences?

I've tried with 166MMX and 233MMX and they both go down to 2.0V and run stable. The 166MMX even overclocks to 208MHz at that voltage. And this gets me guessing if this is normal or the jumpers on my QDI Explorer IV board are not working correctly? 😕 What actually bothers me is that the CPUs aren't any cooler at lower voltages (finger test).

If I get my hands on some Super 7 motherboard then I'd like to see the overclocking potential 😀 and need to get some normal heat sink.

Hi!
What is your Bios version? I have 1.3 which seems to be the last available version, but many years ago someone claimed, without backing it up with a file, there was a beta around with new microcode for K6 and possibly others.
Have you tried K6-2/III?

I'll give it a try as https://forum.hardware.fr/hfr/Hardware/carte- … et_500592_1.htm someone reported (in a list) that it worked with a K6-III.

Nexxen wrote on 2020-03-27, 20:03:

Hi! What is your Bios version? I have 1.3 which seems to be the last available version, but many years ago someone claimed, with […]
Show full quote

kixs wrote on 2013-09-01, 00:02:

I'm wondering if anyone has done any undervolting and what are the experiences?

I've tried with 166MMX and 233MMX and they both go down to 2.0V and run stable. The 166MMX even overclocks to 208MHz at that voltage. And this gets me guessing if this is normal or the jumpers on my QDI Explorer IV board are not working correctly? 😕 What actually bothers me is that the CPUs aren't any cooler at lower voltages (finger test).

If I get my hands on some Super 7 motherboard then I'd like to see the overclocking potential 😀 and need to get some normal heat sink.

Hi!
What is your Bios version? I have 1.3 which seems to be the last available version, but many years ago someone claimed, without backing it up with a file, there was a beta around with new microcode for K6 and possibly others.
Have you tried K6-2/III?

I'll give it a try as https://forum.hardware.fr/hfr/Hardware/carte- … et_500592_1.htm someone reported (in a list) that it worked with a K6-III.

Jan Stubring from Wims bios actively patched many motherboards for k6+ and 128gb support, there is an archive of his site.

I reach out on Wims anytime I need a classic bios update

Good Luck