Date: Wed, 21 Sep 2005 22:59:06 +0200 From: Alexander Konovalenko <kono@kth.se> To: Attila Nagy <bra@fsn.hu> Cc: freebsd-amd64@freebsd.org, freebsd-hardware@freebsd.org Subject: Re: Dual core AMD64 4400+ X2 works fine on Abit AV8 Message-ID: <200509212259.07082.kono@kth.se> In-Reply-To: <43317E28.1090404@fsn.hu> References: <200509211147.17279.kono@kth.se> <43317E28.1090404@fsn.hu>
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On Wednesday 21 September 2005 17.37, Attila Nagy wrote:
> Alexander Konovalenko wrote:
> > 2) recompiled and installed 5.4-STABLE kernel with "options SMP", then I
> > tested it with old single core CPU
> > CPU: AMD Athlon(tm) 64 X2 Dual Core Processor 4400+ (2247.42-MHz K8-class
> > CPU) Origin = "AuthenticAMD" Id = 0x20f32 Stepping = 2
> > Features=0x178bfbff<FPU,VME,DE,PSE,TSC,MSR,PAE,MCE,CX8,APIC,SEP,MTRR,PGE,
> >MCA,C MOV,PAT,PSE36,CLFLUSH,MMX,FXSR,SSE,SSE2,HTT>
> > Features2=0x1<SSE3>
> > AMD Features=0xe2500800<SYSCALL,NX,MMX+,<b25>,LM,3DNow+,3DNow>
> > Hyperthreading: 2 logical CPUs
>
> Can this "I see hyperthreading, while there is no hyperthreading" cause
> performance degradation, for example by HTT defaults to off in the
> recent 5.x builds?
I just made some grep in /usr/src and
found /usr/src/sys/amd64/amd64/identcpu.c, near the line #293:
.....
/*
* If this CPU supports hyperthreading then mention
* the number of logical CPU's it contains.
*/
if (cpu_feature & CPUID_HTT &&
(cpu_procinfo & CPUID_HTT_CORES) >> 16 > 1)
printf("\n Hyperthreading: %d logical CPUs",
(cpu_procinfo & CPUID_HTT_CORES) >> 16);
...
I don't know all details but seem that cpu_feature contain CPUID_HTT bit....
/Alexander Konovalenko
+46-8-5537-8142 (office)
+46-7-3752-2116
http://daemon.nanophys.kth.se/~kono
Royal Institute of Technology (KTH)
Nanostructure Physics Department, Albanova
Roslagstullsbacken 21
10691 Stockholm
Sweden
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