Overclocking Special: The Intel Pentium II 300 SL2W8

Overclocking Of The SL2W8

Now let's get down to it. First of all please realize that since mid 1998 all Intel CPUs are multiplier locked to only the one multiplier they are supposed to run at. This means that a 300 MHz PII comes with a x4.5 multiplier, 66 MHz x 4.5 = 300 MHz. Overclocking this CPU means simply increasing the bus speed, or FSB clock. Luckily, the SL2W8, particularly the one with 4.4 ns L2 cache, runs fine at 100 MHz FSB, making it run at 450 MHz instead of 300 MHz. If you want to try exceeding this you can use the harmless 103 MHz setting, which runs in almost as many cases as the 100 MHZ FSB, or you can try 112 MHz, so that the SL2W8 reaches 504 MHz. I strongly advise against any further increase of the bus clock, as e.g. 124 or 133 MHz, simply because hardly any AGP card will let you run any 3D application without crashing. You also require excellent PC 100 SDRAM with a CAS latency of only 2 ns to achieve that.

I have got 9 SL2W8 CPUs, all from Costa Rica, 40th week of 1998, all equipped with 4.4 ns L2 cache, but not all were the same. I can put them in 5 different categories:

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Serial NumberComments
08400304-0237, 08400304-240Runs at 504 MHz in almost any BX-board that supports 112 MHz FSB
08400304-0239Runs at 504 MHz in many BX-boards with 112 MHz FSB-support
08400304-0238Runs at 504 MHZ in a few BX-boards with 112 MHz FSB-support
08400304-0369, 08400304-0370, 08400304-0377, 08400304-0378Runs at 450 MHz in any BX-board, runs 504 MHz only when voltage raised to 2.2 V, except BH6 runs all w/o voltage change
08400304-0376Runs at 450 MHz in most BX-boards, 504 only in BH6 at 2.2 V

You can see that there are serious differences even though the CPUs are all equipped with the same 4.4 ns L2-cache chips and even though they are have consecutive serial numbers. The 0237 and 0240 are the best chips, the 0376 is the worst of them all.

The result is pretty encouraging, at 450 MHz almost each CPU ran in each board, only 504 MHz are somewhat difficult to reach. The only board that ran all of the CPUs at 504 MHz was Abit's BH6. The reason for that is pretty simple, it lets you raise the core voltage to more than the 2 V default core voltage. Abit's BX6 wasn't as successful as its younger brother, the 0376 CPU failed even at 2.3 V core voltage, which looks as if the BX6 isn't quite as stable as the BH6. However, the BH6 does still not run with the Samsung 6ns 256 MB registered DIMMs.