Don't think too much of it. I have a K6-3+ 400 ATZ that runs at effortlessly 550MHz, but does not want to POST at all at 600MHz. 575 isn't particularly stable either.

All those K6-2+ / K6-3+ CPUs are rated close to their limit. I don't think that it's so unusual that they already produce errors at a 10% overclock. My K6-2+ 570 runs at 600, but not at 610 MHz.

The motherboard can be troublesome too. When I had a FIC VA-503+ (maybe it was 503A), I couldn't get my III+ quite stable at 600 even with plenty of extra voltage. The same CPU is solid at 600 on my ASUS P5A.

Like swaaye said, it's probably your motherboard, or power supply, or both... Doesn't matter how relatively low the power draw of that generation of CPUs are compared to modern CPUs, if the capacitors on the motherboard and PSU are defective, there is no guarantee of stability whatsoever, even if the power draw is low.

I never had a + chip, but after 6 months my old K6-3 450MHz wasn't even stable at 450MHz. I had to run it at 400MHz just to stop all the crashes.
Probably an external problem with my board or PSU or something, but I never figured that out at the time.

Wouldn't go much higher than default voltage. Had Asus p5ab with k6 3+ doing 600mhz no problem (think default was 450mhz). Can't remember but I think voltage was left at default. Actually think I had it undervolted (don't quote me on that). I'd blame your mobo-ram combo for giving you trouble. Only K6 I couldn't overclock much was a K6 2+, couldn't go over 500mhz no matter how much I overvolted it (think default was 450 MHz). K6's were always simple to overclock and easy to find the limit in my case (they can't go much beyond 50 mhz overclock). I've seen reports of k6 3+'s doing 700mhz on Asus p5ab BTW.

shamino wrote:

I never had a + chip, but after 6 months my old K6-3 450MHz wasn't even stable at 450MHz. I had to run it at 400MHz just to stop all the crashes.
Probably an external problem with my board or PSU or something, but I never figured that out at the time.

Bingo! I remember having problems with a K6-2 that wouldn't run stable many years ago and the chip was RMA'd and the slower speed replacement worked fine IIRC... I also concluded retrospectively (albeit much more recently) that it must have been the DTK motherboard or the AT PSU that was the real culprit.

mockingbird wrote:

shamino wrote:

I never had a + chip, but after 6 months my old K6-3 450MHz wasn't even stable at 450MHz. I had to run it at 400MHz just to stop all the crashes.
Probably an external problem with my board or PSU or something, but I never figured that out at the time.

Bingo! I remember having problems with a K6-2 that wouldn't run stable many years ago and the chip was RMA'd and the slower speed replacement worked fine IIRC... I also concluded retrospectively (albeit much more recently) that it must have been the DTK motherboard or the AT PSU that was the real culprit.

They sent a slower chip as the RMA replacement?

The only thing that gives me some doubt about mine is that I know the cooling on that system was poor, so at the time I thought the chip was damaged by heat. Probably not though. I still have that CPU so I really ought to hook it up sometime and test it out.

Only ones here that don`t clock well are the normal k6-2`s (i have the 350, 400 and 500).

k6-3 400 does 500
k6-2+ 533 does 600 (2,1v)
k6-3+ 450 does 600 (2,1v)

For al lot of people 550mhz seems to be the sweet spot as 600mhz isn`t much faster.

Never tried higher. All on asus p5a 1.04 and stable as a rock.

I have 2 of these boards (also a 1.03) and both are perfectly stable at these speeds.

I also have 2 jetway Ali boards, one has mo problems overclocking the same way as the p5a while the other one runs fine with the + cpu`s, it can barely overclock them stable.....

Using good copperbased athlon xp coolers and paste helps a lot too i guess.