Author: Robert Hyatt
Date: 14:17:39 08/27/03
Go up one level in this thread
On August 26, 2003 at 18:38:34, Jeremiah Penery wrote: >On August 26, 2003 at 11:42:03, Robert Hyatt wrote: > >>On August 26, 2003 at 03:00:52, Johan de Koning wrote: >> >>>On August 25, 2003 at 18:04:29, Robert Hyatt wrote: >>> >>>>A single cpu that will run crafty at 1M nps has a cache-cache and cache-memory >>>>bandwidth of X bytes/second. A single cpu that runs crafty at 2M nps has >>>>exactly twice the cache-cache and cache-memory bandwidth and twice the clock >>>>frequency. A dual-cpu just needs two cpus, but the two cpus give twice the >>>>cache-cache bandwidth, but _no_ improvement in cache-memory bandwidth. >>> >>>Nope, C2M bandwith is constant, regardless of n and f (hence constant :-). >> >>Actually it isn't. Some duals use interleaving. Some don't. All quads I >>have here use 4-way interleaving to ramp up the bandwidth significantly. >> >>All machines are _not_ created equal... > >A great many single-CPU motherboards you can buy offer dual-channel memory >and/or 4-way memory interleaving. 1. I don't know much about dual-channel, but it doesn't sound related to interleaving. 2. I have looked at most every single-cpu machine we have here and they are _all_ plain memory boxes (non-interleaved). The easiest way to catch interleaving is to find a requirement that you add two (or four) DIMMS, one per "bank". If you have just one DIMM, or you have just one/two/three DIMM slots, that MB isn't interleaving. > I don't know if many of the SMP (2-CPU, >specifically) boards for Intel or Athlon have that stuff or not. Opteron >doesn't worry about it, as each CPU has its own dedicated (dual-channel) memory, >and N CPUs have N times the aggregate bandwidth of a single-CPU machine. Yes, but Opteron is NUMA, which has its _own_ problem issues to deal with. Anytime you say "each processor has its own memory" you are talking NUMA. I haven't seen any recent Intel MBs that didn't have interleaving. If you don't do that, you take a big performance hit as memory has a hard enough time keeping up with one cpu, much less two, without some sort of bandwidth increasing trickery. All of my quads have 4-way interleaving without exception, going back to my original quad pentium-pro 200 box I still have (ALR Revolution).
This page took 0.05 seconds to execute
Last modified: Thu, 15 Apr 21 08:11:13 -0700
Current Computer Chess Club Forums at Talkchess. This site by Sean Mintz.