Cpu

Can someone please tell me if you can put a 800mhz 100fsb cpu on a motherboard with 133fsb sdram.

Check the motherboard manufacturer website and see the specks. What is the board?

really no way to tell till you provide more information
Use everest to determine what you have if you dont know
http://www.lavalys.com/products.php?lang=en

the answer is YES.

if the board ALREADY HAS USED (has ran using) those EXACT same memory sticks AND the board is NOT "locked" to a 133 FSB then the answer is YES.

133 can run @ 66 / 100 / 133 mhz. speed is determined by the MOTHERBOARD.

as an example: i have TWO DIFFERENT "intel BX chipset" motherboards. BX is able to run (by design) @ either 66 or 100 mhz FSB.

one board is "manufacturer locked" @ 66 MHZ. it will ONLY run P-2's up to 333 mhz and all celerons 533 mhz and LOWER.

the OTHER board is "manufacturer locked" @ 100 MHZ. it will ONLY run P-2 cpu's from 350 to 450, no P-3 support (boardrunner brand board, company "died" ) . the bios chip on this board is 128 kBIT. i have others from this company with a 256kBIT bios chip that DO support P-3 cpu's WITH 512k cache.

i also have an intel i810 chipset board that will ONLY run @ 66 mhz fsb. it will run celeron cpu's up to 733 mhz. the i810's SHOULD support 100 and 133 fsb. but the manufacturer of the BOARD decided to not enable it.

bottom line: if the ram worked on that board in the past @ 133, it WILL run @ 66 and 100 mhz fsb.

EDIT: i posted before i finished typing.

I have to disagree with tjj to some extent. 133 SHOULD be able to run at 100 and 66 but some particularly the most recent stuff will not. Paticularly at 66. Usually it will run at 100 but I have encountered some that has problems running at 100 also. This aplies to the ram but I have not seen a board that supported 133 that won't support either 100 or 66..