Status of hyperthreading in FreeBSD

Ivan Voras ivoras at
Mon Dec 22 20:31:55 UTC 2008

Wojciech Puchar wrote:
>> Atom's HTT is actually pretty good - I saw up to 25% more performance
>> simply by using multithreading in 7zip's compression benchmark (on
>> WinXP, though). Of course, OTOH it uses about that much more transistors
>> on the CPU die so it's not exactly free performance.
> really that much? i thought maybe 1-2% (just 2 sets of registers).

Screenshots are available :)

I was also surprised because in this case both threads use the same
algorithm with the same requirements on registers. It used to be (in the
days of Pentium 4) that HTT would work best if the two threads used
different sets of instructions and registers (e.g. one doing integer
math and another doing floating point math). I guess they made more
effort this time.

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