Author: Anthony Cozzie
Date: 23:10:50 11/17/02
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On November 17, 2002 at 13:58:43, Vincent Diepeveen wrote: >Hello, > >If i read the below section of the intel programming guide very well, >then i interpret that as: > > a) only the Xeon MP has hyperthreading and not the normal P4s, > not even P4s sold as Northwoods. > > b) even the Xeon MP you should not assume that it supports hyper > threading. In fact something that gets sold as Xeon MP you should > still not assume that it supports hyper threading, but instead > one must assume that only after specifically questionning the cpu > whether it can do it. > >Intel IA-32 programming manual. Page 247 (of 780): >" >7.6.1 Implementation of Hyper-Threading Technology in IA-32 Processors > >Intel's Hyper-threading Technology was introduced into the IA-32 architecture >in the Intel Xeon processor MP and in the later steppings of the Intel Xeon >processor. Both of these processors implement Hyper-Threading Technology with 2 >logical processors per physical processor. When reading the following sections >(and other sections in this book that refer to this technology), assume that all >references to the implementation of Hyper-Threading Technology in the Intel Xeon >processor MP also apply to those later steppings of the Intel Xeon processor >that implement Hyper-Threading Technology. > >Intel recommends that software not rely on IA-32 processor names to determine >whether a processor supports Hyper-Threading Technology; but instead, it should >use the CPUID instruction as described in Section 7.6.5, "Detecting >Hyper-Threading Technology". >" > >Vincent All P4s have hyperthreading. You don't maintain "multiple build targets" for a CPU, or any other ASIC for that matter :) However, most of them have it disabled. anthony
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