The original athlons came in slot A format. They had 512k L2 cache on the cartridge which ran at 1/2 the clock of the processor. As the clock speeds of the processor increased the speed of the L2 cache was not able to maintain the 1/2 ratio and became a smaller percentage of the processor clock.
The Athlon TB has 256k L2 cache running on die at full speed. It improves performance about an average of 10% compared to the same clocked athlon classic. Most of these processors come in the socket A format, but some are produced in slot A.
For the moment, both the athlon classic and TB have external speeds of 100mhz DDR (effectively 200mhz). Soon a 133mhz DDR TB will be availble.
SlotA processors work in the AMD 750 (accepts 100mhz memory) or VIA kx133 (accepts 133mhz memory). However, slot A TBs do not work in the Kx133, atleast not reliably.
The popular socket A platforms are the VIA KT133 and KT133A. Basically the KT133 is a socket a version of the KX133 and the KT133A allows a 133mhz DDR FSB. Also, there are some chipsets that support DDR memory comming out soon.