N=4 or 5, but I had similar experiences. My first Mendocino, back in 1999, was a 366. I was hoping for 550MHz but couldn't get it stable over 500MHz. Later tried a range of them (both slot and socket versions) and always hit walls around 500MHz with low-multiplier CPUs. I know that some people got more, but you needed a boatload of luck. Of course they were actually sold up to 533MHz, so I guess there was a lot of binning going on.

Note that doing two at once is more challenging than a single CPU, so the BP6 isn't helping here 😉

I used to have a Mendocino Celeron 466. The best I could do was 525 (7x75).
As far I know the 533 was the fastest Mendocino released, so that must have been as far as the architecture could go.

H3nrik V! wrote on 2025-09-05, 09:12:

So, I have an ABiT BP6, which I was gonna do an "unlimited (for it's time) power" build, as in fully loaded with 3x256 MiB memor […]
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So, I have an ABiT BP6, which I was gonna do an "unlimited (for it's time) power" build, as in fully loaded with 3x256 MiB memory and the fastest CPUs available.

Running for years back in the day with a couple of 366s at 550, I figured that 600 was doable with some 400s, so I bougt a total of 9 specimens ..

Running a test rig with an ABiT BH6 1.01, 2x256 MiB PC133 and a Gigabyte GA6R7 slotket with an Alpha PEP66 cooler on, I started binning.

But utter lemons. Out of 9 CPUs, 3 couldn't run a full memtest86 (Yes, I had tested the memory using a 100 MHz FSB CPU beforehand), 2 couldn't even execute memtest86 and the last 4 didn't even POST at 600.

Voltage was tried all the way up to 2.3V - I even fiddled with L2 Cache latency for at least one of the CPUs, but to no avail.

Is it just so, that 550 is how far the architecture scales, or did someone have more luck?

I managed 600 on one of my S370 300A's, one of about a dozen IIRC.

Didn't do "24h prime" on it, but it managed all of my other usual benchmarks, including a 1h render.

But on a BP6? I doubt it.
Mine was on a BX6 R2 I think, a way better overclocker then the BP6.
In fact the reason I found the 600MHz gem was that I was binning all my Mendocinos to find the best ones for my BP6 =)

bofh.fromhell wrote on 2025-09-05, 10:49:

I managed 600 on one of my S370 300A's, one of about a dozen IIRC. https://i.imgur.com/UYuUw8I.jpeg […]
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H3nrik V! wrote on 2025-09-05, 09:12:

So, I have an ABiT BP6, which I was gonna do an "unlimited (for it's time) power" build, as in fully loaded with 3x256 MiB memor […]
Show full quote

So, I have an ABiT BP6, which I was gonna do an "unlimited (for it's time) power" build, as in fully loaded with 3x256 MiB memory and the fastest CPUs available.

Running for years back in the day with a couple of 366s at 550, I figured that 600 was doable with some 400s, so I bougt a total of 9 specimens ..

Running a test rig with an ABiT BH6 1.01, 2x256 MiB PC133 and a Gigabyte GA6R7 slotket with an Alpha PEP66 cooler on, I started binning.

But utter lemons. Out of 9 CPUs, 3 couldn't run a full memtest86 (Yes, I had tested the memory using a 100 MHz FSB CPU beforehand), 2 couldn't even execute memtest86 and the last 4 didn't even POST at 600.

Voltage was tried all the way up to 2.3V - I even fiddled with L2 Cache latency for at least one of the CPUs, but to no avail.

Is it just so, that 550 is how far the architecture scales, or did someone have more luck?

I managed 600 on one of my S370 300A's, one of about a dozen IIRC.

Didn't do "24h prime" on it, but it managed all of my other usual benchmarks, including a 1h render.

So they do exist 😀 mine failed within few minutes in memtest86, and didn't get to render any images in 3DMark2001

Anonymous Coward wrote on 2025-09-05, 10:39:

I used to have a Mendocino Celeron 466. The best I could do was 525 (7x75).
As far I know the 533 was the fastest Mendocino released, so that must have been as far as the architecture could go.

Yes, 533 was the fastest sold, so probably the wall was close to that. It could have been a political decision, though, but it seems to be the max.

I have a pair of 366 that are completely fine at 550, so they'll probably be the weapon of choice for the BP6 now all 9 400 failed ... 🤣

bofh.fromhell wrote on 2025-09-05, 10:49:

But on a BP6? I doubt it.
Mine was on a BX6 R2 I think, a way better overclocker then the BP6.
In fact the reason I found the 600MHz gem was that I was binning all my Mendocinos to find the best ones for my BP6 =)

Looks like this came in an edit? The BP6 works brilliant overclocking 366s - I know the BX6 was famous, but wasn't BH6 even more? Or was it just the fact that it was cheaper that made it the board of choice for overclocking in '99?

bofh.fromhell wrote on 2025-09-05, 10:49:

I managed 600 on one of my S370 300A's, one of about a dozen IIRC.

And now I see it was a 300A. That's truly impressive, probably binned much lower than a 400 was, and then at 133 FSB. Must've been crazy in its heyday ..

H3nrik V! wrote on 2025-09-05, 10:58:

bofh.fromhell wrote on 2025-09-05, 10:49:

But on a BP6? I doubt it.
Mine was on a BX6 R2 I think, a way better overclocker then the BP6.
In fact the reason I found the 600MHz gem was that I was binning all my Mendocinos to find the best ones for my BP6 =)

Looks like this came in an edit? The BP6 works brilliant overclocking 366s - I know the BX6 was famous, but wasn't BH6 even more? Or was it just the fact that it was cheaper that made it the board of choice for overclocking in '99?

Eventually I found 2 366's that would do 550 in my BP6.
But they need 2.2v in the BP6 and 2.0/2.1 in the BX6.
In fact most of my 366's would do 550 in the BX6 but only 2 out of 8 or so would do it on the BP6 at less then 2.3v.

bofh.fromhell wrote on 2025-09-05, 11:11:

Eventually I found 2 366's that would do 550 in my BP6. But they need 2.2v in the BP6 and 2.0/2.1 in the BX6. In fact most of my […]
Show full quote

H3nrik V! wrote on 2025-09-05, 10:58:

bofh.fromhell wrote on 2025-09-05, 10:49:

But on a BP6? I doubt it.
Mine was on a BX6 R2 I think, a way better overclocker then the BP6.
In fact the reason I found the 600MHz gem was that I was binning all my Mendocinos to find the best ones for my BP6 =)

Looks like this came in an edit? The BP6 works brilliant overclocking 366s - I know the BX6 was famous, but wasn't BH6 even more? Or was it just the fact that it was cheaper that made it the board of choice for overclocking in '99?

Eventually I found 2 366's that would do 550 in my BP6.
But they need 2.2v in the BP6 and 2.0/2.1 in the BX6.
In fact most of my 366's would do 550 in the BX6 but only 2 out of 8 or so would do it on the BP6 at less then 2.3v.

So, I probably just got lucky back then 😀 Albeit AFAIR they needed 2.1/2.2 to run stable - but who cared, as long as they were stable. Once in a while I used SETI@home to help heating up my room in the off-season when the house's heater was shut down 🤣