[geeks] AMD64 compiler flags

[Charles Shannon Hendrix]

Sat, 06 Nov 2004 @ 11:29 -0800, Francisco Javier Mesa-Martinez said:

> On Sat, 6 Nov 2004 10:56:19 -0500
>  Charles Shannon Hendrix <shannon at widomaker.com> wrote:
> >Tue, 26 Oct 2004 @ 15:53 -0700, Francisco Javier 
> >Mesa-Martinez said:
> >
> >>the math flags for mmx and sse are useless, as is 
> >>-march=k8 depending 
> >>on which gcc version you are using. 
> >>                                 
> >
> >Why do you say mmx and sse are useless? 
> 
> In the AMD64 target at this point they're useless... 

What about 3DNow?  I assumed the new version of 3DNow was created
specifically for the 64-bit mode.

I don't see any gcc flags for that yet.

> If you are targetting a 32bit x86 like P4 et al, I believe that yes
> indeed you can get some nice code out of those flags. Sorry if I
> wasn't specific about that.

OK.

> >What I'm curious about is how the system managed to run 64-bit execs
> >on a 32-bit OS.
> 
> Huh? Never claimed to have done such thing, 

I know, which is why I didn't say you did... :)

I'm asking how the system (I should have said "a system") runs 64-bit
execs on a 32-bit OS.

For example, the game Far Cry and Unreal Tournament 2004 both come with
64-bit versions if they detect an AMD CPU, and Windows is a 32-bit OS.

Does the AMD64 CPU allow all of the 64-bit operations except addressing
or something like that?

> >I thought about playing with a 64-bit BSD or Linux distribution, but
> >haven't really researched it much yet.
> 
> Then you need to get a 64bit distro and kernel ASAP, the 
> speed difference is SIGNIFICANT at least in our 
> experience. :) At least most of the machines I am using 
> for simulation are Xeons with the 64bit extensions and we 
> are getting some very nice performance out them with 64bit 
> 2.4 kernels.

I got quite a boost just compiling Linux for the AMD64.

I might try a 64-bit distribution when I get a drive to experiment with.

One interesting thing about this upgrade: my old SCSI controllers
(Adaptec 2940s) are now a serious bottleneck.


-- 
shannon "AT" widomaker.com -- ["And in billows of might swell the Saxons
before her,-- Unite, oh unite!	Or the billows burst o'er her!" -- Downfall
of the Gael]