On 1/11/06, Jon Nelson
On Wed, 11 Jan 2006, Joachim Schrod wrote:
Hello,
I have a system with a Pentium P4 and an Intel D865GBF mainboard. The CPU has hyperthreading, but this is disabled in the BIOS. (The system got delivered that way. I bought it w/o any operating system.)
Nevertheless, SUSE 10.0 seems to detect Hyperthreading, since it uses an SMP kernel. Also, /proc/cpuinfo contains the lines
model name : Intel(R) Pentium(R) 4 CPU 3.00GHz stepping : 1 cpu MHz : 2993.250 cache size : 1024 KB physical id : 0 siblings : 2 core id : 0 cpu cores : 1
where -- as far as I understood -- a `siblings' line with a value >1 denotes hyperthreading.
So, is it necessary to enable hyperthreading in BIOS, or does Linux just ignore that setting and utilizes the CPU's full capabilities anyhow?
Yes, enable it if you want to take advantage of it. However, of late there have been some interesting articles that suggest that turning hyperthreading *off* may be faster than having it on.
Interestingly, most articles are controversial, some of them
suggesting turning it off others claim to have achieved performance
improvements of more than 30%.
Besides this, Intels HT-enabled processors suffer from a security
design flaw allowing unprivileged users to steal an RSA private key
being used on the same machine as an exploit showed at BSDCan05. Read
more about it in http://www.daemonology.net/papers/htt.pdf.
\Steve
--
Steve Graegert