no, thats actually what it means, or at least there were joint ads when it came out promoting the xp and winxp for superior compatability. thats why i believe intel finally made the move to crush amd, because very shortly after those ads came out intel was pressing hard for the demise of amd and still might succeed. seeing as how joe six pack might get the idea that wintel was no longer the monopoly that it was supposed to be scared intel more than the fact that amds were the top performers at the time. this is all just my .02$ of course
Marketing - You tweak the OS for the hardware not the other way around. Although AFAIK AMD and M$ did work together a lot before win xp came out to ensure compatabilty and good performance... Don't forget there was a windows update patch for athlon XPs shortly after win xp came out; more to do with M$ then AMD I am sure.
It's KB, as in kilobytes and it's split into two groups - Instructions and Data so for the XP the L1 is 128K, 64KB data and 64KB instructions. The P4 as 8KB for data and 12KB for instructions but it's a different design so don't read too much into the cache sizes for the L1.
Completely marketing - in fact when they first came up with XP it had nothing to do with Windows XP - the XP was for extra performance. Then they decided it would make more sense to say it was tweaked for windows XP. Hell there isn't anything tweaked for windows. If you want something tweaked go with an AMD tweaked linux kernel.