Author: Robert Hyatt
Date: 05:31:49 11/22/05
Go up one level in this thread
On November 22, 2005 at 03:13:03, Terje Vagle wrote: >After further checking, you will get 4 threads with the new Intel D840 extreme >edtition. This cpu has 2 cores and Hyperthreading enabled thus giving 4 threads. Yes and no. Yes it will supposedly have hyper-threading. But no, that does not exactly translate into two extra cpus. It basically translates into two cpus that are further sub-divided into two 1/2 cpu (performance-wise) units. Almost every chess program will do better on a dual that is 2x faster than on a quad. For example, I'd take a dual 3ghz over a quad 1.5ghz every time, because of the parallel search overhead. For Crafty specifically, the math goes like this: A hypothetical single processor with hyperthreading disabled, using a single thread, will produce a NPS value of 1.0M. And it will take 100 seconds to search to a fixed depth, searching a tree of 100M nodes. Turn on hyperthreading and the NPS will rise to 1.1M, or .55M per logical processor. Unfortunately 30% of one processor is wasted due to parallel search overhead (extra nodes searched). So the effective aggregate performance is .55M + .7*.55M = .935M, which is actully slower. If this actually has one shared L2 cache, that will be a further performance bottleneck when compared to the opteron dual-cores which have dual L2 caches as well. > >Snap from toms hardware: > >Although the new processor's codename Smithfield implied a completely new >design, the reality is that the CPU consists of two Prescott cores with 1 MB of >L2 cache; no features such as additional instruction sets were added. The >regular Pentium D also lost its Hyper Threading capability, which is an >exclusive feature of the Extreme Edition, making this the only difference >between the Pentium D and the Pentium EE of the 800 series except for the latter >coming with a freely selectable multiplier. The latter is only available as the >840 model running at 3.2 GHz.
This page took 0 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.