[Tfug] Dual cores and hyperthreading

[John Gruenenfelder]

Hey all,

I've got a hardware question about dual cores and hyperthreading.  My new
laptop has a core duo chip inside.  To utilize both cores, all you need is a
SMP kernel.  Easy enough.

But, the core duo is also based on the Pentium 4m which supports
hyperthreading.  This is confirmed by running cpuid:

---------
Extended brand string: "Genuine Intel(R) CPU           T2400  @ 1.83GHz"
CLFLUSH instruction cache line size: 8
Initial APIC ID: 1
Hyper threading siblings: 2

Feature flags bfe9fbff:
...
SS     Self Snoop
HT     Hyper Threading
TM     Thermal monitor
...
---------

Is is possible to take advantage of this as well?  My understanding is that
hyperthreading is 2 virtual CPUs in a single core and so it should be separate
from the hardware which enables two physical cores thus making it possible to
use both at the same time.

Last time I used a HT capable machine in Linux (a while ago), I didn't need
anything extra other than an SMP kernel.

Am I confused about the situation?  Maybe I need additional support from
elsewhere in the machine like the BIOS (I already looked in there)?


-- 
--John Gruenenfelder    Research Assistant, UMass Amherst student
                        Systems Manager, MKS Imaging Technology, LLC.
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