All Thunderbird chips are identical, besides from tiny little flaws that decide how how fast a certain chip can operate. The only difference between an overclocked 800Mhz and a chip that is rated at 1Ghz is that the 800 possibly gets a bit hotter. The performance is exactly the same.
Though there is the slight (teeny-tiny) chance that the reason that it's labeled as an 800 and not as a 1GHz is because the chip just as too many tiny flaws to run stable at 1GHz.
But then, such are the risks of overclocking.
Besides, it'd be pretty unlikely that an 800 wouldn't overclock to 1GHz.
It will be the same performance, but watch out for heat and temperature problems if you are going to clock - they'll destroy your processor just like that if unwatched.
Rob
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