CPU's: SL7EP vs SL7SA

[sojourner]

I upgraded the CPU in my T41 from a 1.6 GHz Banias to 1.7 Dothan (SL7EP). Just found out today there exists a very similar model to that Dothan, it is the SL7SA.

To the best of my knowledge the differences are:

SL7EP = 1.7GHz, 400FSB, no Execute Disable Bit
SL7SA = 1.73GHz, 533FSB, Execute Disable Bit

So some questions arose, like what is a Execute disable bit and are there any performance improvements if you put a 533FSB CPU into a MOBO designed for a 400FSB?

[aaa]

A 533 fsb cpu won't work at full speed in a T41. Any cpus with XD enabled (even if they're 400) are not in the T41 bios, meaning you have to do a few tricks to get those to work. The XD bit is a security feature, basically it makes it harder for various security exploits to work. Theoretically, this would make it harder for your computer to infected by viruses, but I haven't heard any concrete stats on this (and only a few viruses would be blocked by this).