Re: Hyperthreading Issues (on Athlon64?)
John Baldwin <[email protected]>
| Newsgroups | gmane.os.freebsd.devel.smp |
|---|---|
| Message-ID | <[email protected]> |
On Tuesday 10 October 2006 14:55, JoaoBR wrote: > On Tuesday 10 October 2006 15:11, Brooks Davis wrote: > > > My dmesg does not have the line about "Hyperthreading: 2 logical CPUs", > > > though. But I had been pretty sure the Athlon64 chips didn't have any > > > hyperthreading support. Why is the HTT there? > > > HTT is NOT hyperthreading, HT is and HT does not exist on AMD64 Err, no. The HTT there stands for HyperThreading Technology. I should know as I added it. :) What it really means is that you can check one of the registers returned by cpuid 1 to see how many logical CPUs the current physical CPU package contains. Originally this was only used for hyperthreads, but it was reused for multi-core as well, so if you have a dual-core chip with 2 hyperthreads in each core, it reports 4 logical CPUs. If you have 2 cores, it reports 2 logical CPUs. If you have 1 core with 2 hyperthreads, it reports 2 logical CPUs. -- John Baldwin _______________________________________________ [email protected] mailing list http://lists.freebsd.org/mailman/listinfo/freebsd-smp To unsubscribe, send any mail to "[email protected]"