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wbmw

05/11/05 12:05 AM

#55889 RE: pgerassi #55886

Re: Xeon, requires a bridge chip between FSBs after 4 way. That isn't glueless

But Opteron needs a bridge chip after 8-socket, so what difference does that make? I think Tenchu is arguing more on the basis that even Opteron needs additional chipset logic before you can make a platform. You can't just string the CPUs together "gluelessly" and expect it to make a computer. You can't even be miserly over the number of companion chips, or else you end up with something that's under powered in I/O.

By the way, the strength in Opteron doesn't come from talking directly to other Opterons, it comes from offering the best trade off between system bandwidth and average system latency to main memory. The data in an Opteron system only passes through the CPUs before reaching its destination in memory, so I consider that the more important metric. Besides, even Xeons on the same bus share signals that "talk" between CPUs, but it's how they interact with memory that makes all the difference. Unfortunately, all the Xeons on the same bus have to share the same path to main memory, which presents a bottleneck, while Opteron does the right thing by offering multiple pathways to local and remote memory. Intel will eventually have to offer something similar to stay in the game.
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Tenchu

05/11/05 2:22 AM

#55893 RE: pgerassi #55886

Pete, as usual, you have to type an entire essay just to squirm your way out of all the links I provided. And it only took me a few minutes to do a search on Google.

Just to throw you on another loop, here are more links on Google referring to the "glueless" Xeon:

http://www.dewassoc.com/systems/component/intel/bx80525ky5501m.htm

Support for glueless 4-way SMP operation and scalability to 8-way and above multiprocessor configurations with clustering technologies.

http://www.sharkyextreme.com/forums_spotlight/18/2.shtml

While the Pentium III has 256KB L2 and can support 2-way multiprocessing, the Pentium III Xeon supports up to 2MB of L2 cache (all on die), and up to 4-way glueless multiprocessing. By glueless, I mean on a single bus. One of Intel's chipsts called the ProFusion supports up to 8 processors, but that is through additional "glue" logic.

http://www.theinquirer.net/?article=19495

Step back in time to Nov. 1 1995 and the debut of the Pentium Pro. This chip is the direct ancestor of the Pentium M, and if you read the spec sheets, you will see it could do glueless multiprocessing up to four CPUs.

Tenchu