FreeBSD 64-bit(EM64T) and Hyperthreading support

[Fluffles]

You Wrote:
> I wonder if I could benefit from these features when running AMD64
> version. On i386 install, I just enabled SMP and the OS happilly
> reported 2 logical cpus, however, I'm not sure how I will build a
> particular application to benefit from this hyperthreading thing.

Not all applications do. In fact, HyperThreading can cause lower
performance in a lot of situations. Moreover it poses a (minor) security
risk to your system. I also have read HyperThreading is disabled by
default for that reason, but that might be old information.

> There are certain knobs when configuring a particular application
> that says --enable-pthreads. Does it have something to do with this
> HT thing? Is it a bad idea to always "pkg_add" rather than "make
> install"??

Using packages means the package is built for all CPU types and without
optimizations. With ports you can use the "optimized C-flags" feature,
which causes "make" to compile using all supported optimizations like
SSE/SSE2, etc.

> Also, I'm concerned with EM64T. Let's say I installed the AMD64 version,
> those software I will be building via
> ports will pick up this EM64T thing, right??

Since Intel's EM64T is a shameless copy of AMD's AMD64 technology
(without any mention to "AMD64" in the docs) -- yes you should be able
to run the FreeBSD AMD64 platform without any problems.

> Enhanced Intel Speedstep Technology - I think this has something to do with
> overclocking.. still need to check on their site.

Nope, it will cause lower power drain by lowering the clock frequency
and voltage when the processor is sitting idle. You'll need the cpufreq
kernel loadable module installed (kldload /boot/kernel/cpufreq.ko) and
run "powerd" iirc. But as far as i know Intel hasn't come to the level
of Cool'N'Quiet in recent AMD processors. I'm not sure if the SpeedStep
desktop processors can actually do voltage control.

Good luck!

- Veronica