I just got rid of a similar system. I busted a pin from the CPU so it would be detected as 100MHz bus, and VIOLA, it was detected as a Celeron 900. Worked perfectly I might add.
That system came from the factory with PC133. I pulled it, and put in PC100, so I could use the PC133 in a faster system.
PC133 and PC100 are both backwards compatable to 66MHz. In fact, PC133 being more common now, it's cheaper. And a lot of PC100 is just relabled PC133, since PC100 has been out of production longer.
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