Archived from groups: alt.comp.hardware.overclocking (
More info?)
Phil Weldon wrote:
> I assume you wish to overclock. The Pentium II has an off-chip L2 cache
> which much also be cooled, so doing anything to the CPU thermal surface
> still leaves the problem of the L2 cache. Also, the Pentium II is not going
> to be such a speed demon. The slowest Pentium II CPUs are based on a 66 MHz
> FSB (with an unlocked, or limited multipler.) These, I think, topped out at
> 333 MHz. The faster Pentium II CPUs had a 100 MHz FSB, and while the 350
> MHz Pentium II had an unlocked multiplier, the 450 and up had locked
> multipliers. I think there might have been a Pentium II 550, but perhaps
> the top speed was only 500 MHz.
The PII was 233Mhz - 450Mhz, 450 was the only speed that 'overlapped'
with the PIII.
PII 233Mhz - 333Mhz were all 66Mhz FSB with unlocked/limited multiplier.
350Mhz - 450Mhz were all 100Mhz FSB, and all were multiplier locked AFAIK.
IME the off-die L2 cache was the overclock limiter on all PIIs, you
could always go further with L2 disabled - but there was no point in
doing so and the L2 rarely, if ever, responded to efforts to improve
heat transfer.
> At any rate, a Pentium II 350 will
> overclock to maybe 550, but that's it no matter what you do. A better
> choice would be an SECC2 Celeron 300a or maybe a Celeron 366. These CPUs
> have only 1/4 the L2 cache size as the Pentium II, but the L2 cache is on
> the same chip as the CPU, and runs at the full CPU speed, rather than half
> the CPU speed as the Pentium II CPUs do. The Celeron (pre 'Coppermine')
> was produced with speeds up to 533 MHz, all using a 66 MHz FSB.
> Overclocking the Celeron 300a is just about the easiest overclock there is;
> just force the FSB to 100 MHz, and there you are, running at 450 MHz with
> everything stock (well, maybe a slight core voltage increase, but certainly
> nothing but the stock Intel supplied cooling.) The Celeron 366 at 550 MHz
> is about as high as you can expect to go with a pre 'Coppermine' CPU, but
> both of these overclocks allow standard PCI and AGP bus speeds with a 50%
> overclock of the FSB because you just increase the FSB to a standard 100
> MHz.
>
> You can do all sorts of nice lapping on the heat slug for an SECC2 Celeron,
> but it's not really necessary in most cases (though some slugs were a bit
> concave.)
>
> Bottom line, try to get 550 MHz out of a Pentium II, but don't invest any
> time in changing the heat transfer surfaces; it will be complex, and not
> worth the trouble - if you just gotta do it, use a better heatsink and fan
> attached to the spreader plate in the Slot 1 Cartridge that contacts both
> the CPU slug AND the L2 memory chips. Better yet, find a Celeron 300a or
> 366, and lap to your heart's content.
>
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