Scumbria, <Besides the high speed core, Willamette has a 400 MHz bus. It should be a great server CPU, and will probably make IA-64 much less attractive than it already is.>
1) Foster is the server version of Willamette. Name games, you know.
2) The Willamette/Foster bus is actually a 100 MHz bus, but the data bus is quad-pumped to 400 mega-transfers per second. The problem with a 4x bus is that the turn-around cycle from one transaction to the next is still a full 100 MHz clock, meaning four potential transfers are lost in the cycle. So in a 4-way Foster system, that 4x bus will not be as "efficiently" used as a 1x or 2x bus.
3) Merced has a 133 MHz bus with a double-pumped data bus. Although the theoretical max bandwidth of the Merced bus is 2/3 that of the Foster bus, it should be used rather efficiently.
4) The Merced bus features an "enhanced defer" feature which allows deferred transactions to be retired with less latency than before. Foster doesn't have this.
5) 4-way Merced systems will be introduced before 4-way Foster systems, I think. Merced's chipset, the 460GX, is already at a high level of maturity. I have very little info on 4-way Foster chipsets, however.
6) If all else fails, well, there's always McKinley!
Tenchusatsu |
