[linux-audio-user] AMD64 with Linux audio applications?

[Noah Roberts]

On Mon, 21 Mar 2005 13:41:41 -0500, Ivica Ico Bukvic <ico at fuse.net> wrote:
> > I have an amd64 running in 64 bit mode.  There honestly isn't much
> > reason to get a 64 if you are going to run in 32 bit mode...They are
> > way more expensive than the 32 bit counterparts and don't offer enough
> > extra in 32 bit mode.
> 
> FWIW, I strongly disagree. You get much better performance per clock on a
> 64-bit machine even when running in 32-bit simply due to chip architecture
> improvements including SSE2 among other things, and the price should not be
> that different when compared with the 32-bit offering (as long as you don't
> go for the FX stuff). Also, heat dissipation as well as battery life (if
> considering laptop) is definitely a plus when compared with Pentium4
> offering. Pentium-M processors are also nice but also generally more
> expensive.

I am of course not talking about Intel processors, which are always
way overpriced, when I compare price between 64bit and 32bit.  Maybe
the prices of 64 AMDs has gone down considerably but when I bought
mine the price was at least 5x greater than a 32 bit at the same
speed.

BTW, I am pretty sure the SSE2 registers are only available in 64bit
mode.  I used the amd64 as my target platform in my os "design" for
college.  If I recall correctly the SSE2 registers are one of many
things that become unavailable in 32bit legacy mode (the mode used
when you run a 32 bit OS), and this includes the expanded memory
addressing.  In compatability mode, where the os is 64bit but the app
is 32, they might be available.  I could have my mode names
reversed...

In short, when you run the 64bit processor as a 32bit processor you
loose almost all of the enhancements made in the new design.  You
probably actually have better features with an actual 32 bit processor
than you do with a 64 in 32 mode.