Are you sure that the sempron is still based on the XP core? I thought the went to a crippled 64 when they went to the socket 754 platform, you know with the integrated memory controller, and then the 64 bit. Or are these just xps with an integrated memory controller and 64 bit tacked on.
It seems that it would be more expensive to do it that way then to just disable some cache on a 754 chip that had some problems in the cache.
But then again I am just a newbie and you are one of the great ones, right?