<< The T-Bred laptops actually have 512k of cache instead of 256k. Hopefully the desktop version will feature the extra cache too. >>
It's a myth.
The Throughbred Mobile's contain the same 256K L2 as their desktop counterparts will, and at least initially will continue to utilize the 200MHz FSB the Palomino mobile processors do.
The desktop Throughbred also has a 256K L2 cache, and similarly the same 266MHz FSB of their predecessors.
AMD has already confirmed as much, and they also reported that Compaq et al was incorrect and in fact the suppoed 'Throughbred' Compaq was advertising wasnt even a Throughbred at all, but merely the same Palomino core we can already purchase.
Regarding TBred launch, the Desktop Throughbred isnt expected to launch until late Q2 2002, so your likely looking at the mid-point of June before it's officially available.
Rumours of the speed at which it will launch vary from early reports of 2200+, to more recent reports of 2400+.