The Hammers will have a memory controller onboard, so they will have a low-latency connection to the system RAM, but can also function with a motherboard-based memory controller if desired. It will be the first AMD CPU to feature SSE2 enhancements, and variants will be available for single-processor, dual-processor and higher multiprocessing setups. It will perform better on a clock-for-clock basis than the current AthlonXP.
System RAM will be DDR333 memory, last I heard.
One interesting and pleasing tidbit: the heatsink is apparently going to be fully symmetrical. You cannot put it on backwards (yay! says mechBgon
). It will screw into a very burly all-metal bracket. This should put to rest any fears of socket lugs breaking off.
The CPUs will also have massive integrated heatspreaders. This is an excellent feature because even if the system were accidentally started with the heatsink missing, it would take time to heat up the mass of the heatspreader, allowing the system to catch the emergency on a gradual ramp, rather than a sudden spike. And obviously, the heatspreader will prevent damage to the core.
There have been some scattered benchmarks of Hammer prototypes. Too early to say how it will do compared to what Intel will have out this fall, but the addition of SSE2 may help it a lot in the benchmarks where the P4's SSE2 enhancements put it out front.