Joshua Baker-LePain <jlb17 at duke.edu> wrote: > One has to be even more careful with terminology these > days. You can see less memory bandwidth per *core* with > dual core Opterons. Correct. > But, as you point out, each CPU (socket -- what should we > call it?) Yes, that's what I try to do. S[ocket]940. > has, essentially, its own bank** of memory. S754 has one (1), glueless, 184-trace 64-bit DDR channel**. S939/940 has two (2), glueless, 184-trace 64-bit DDR channels.** _All_ other PC sockets do not have memory channels. They have a "front side bus" (FSB) to a bridge. Many of these lines are multiplexed with others. All Intel GTL platforms bridge into a "hub" all components share -- hence Memory Controller Hub (MCH). Intel S370 and 478 (not to be confused with S423, which uses Rambus, long story) and others have logically (data-wise, which may be muxed with address, control, etc...) _only_ one (1) 64-bit memory channel. Any "dual channel" marketing is an interleaving hack done at the MCH. Intel S603, 604 and 775 logically have two (2) 64-bit memory channels. Intel sometimes "widens" the GTL logic at the MCH for 4-way servers, although that requires additional support. Digital EV6 platforms have ports (up to 16) into a "crossbar switch." The logical front-side bus is also 64-bit, including S462. Again, any claims of "dual DDR" is actually an interleaving hack, done in an attempt to reduce latency and increase overall throughput. But it is not the same as S939/940's _true_ 368 traces for a _true_ 128-bit DDR. [ **ANAL NOTE: The term "bank" in traditional PC/RISC architecture actually 32-bit. So a 64-bit DIMM is 2 banks. ] BTW, AMD multi-cores simply use an internal HyperTransport. They are ultra-simple to design. Intel, on the other hand, uses a bridge for dual-core, which has massive limitations. This is why Intel is moving towards dual-ported FSBs, because it's just an evolution of what they've done with dual-core internally to the IC package. -- Bryan J. Smith | Sent from Yahoo Mail mailto:b.j.smith at ieee.org | (please excuse any http://thebs413.blogspot.com/ | missing headers)