[nylug-talk] AMD 64 BIT questions

[jh]

anthonyriga wrote:
> I am thinking about putting together new pc and see
> there alot of good prices on AMD processors 64bit. I
> am most familiar with 32bit systems running Linux
> Fedora 5. Few questions I have 
>    Can a 32 bit version of Fedora 5 be installed on
> 64bit AMD processor? 

Already answered, but yes, you can run 32-bit anything on the 64-bit stuff.

>    Is there an more speed advantage to using the 32bit
> os on the 64bit processor?

This was also already answered, but...

Depending upon the 64-bit CPU that you choose, you may be giving up 
speed by not running a 64-bit OS (or, actually, vice versa). My 
experiences, and this is anecdotal (and backed by some benchmarks that 
I've read):

* Pre-"core" Intel 64-bit stuff: runs 32-bit stuff faster than 64-bit.
* Athlon64/Opteron: runs 64-bit stuff faster than 32-bit. Moreover, I've 
seen a mild performance increase for pre-compiled 32-bit binaries 
running on a 64-bit OS (at least, under Gentoo, about 10% in one CPU 
intensive commercial app).
* Intel "core": I've yet to see any comparison under 64-bit OS's; this 
may be partially why Intel is kicking AMD's a$$ in online comparisons - 
AMD runs best as a 64-bit proc. Not sure if the new Intel stuff does 
(I'd assume so).

>   If I do use the 64bit os what catches would I need
> to look out for? I have heard of people complainig
> about driver issues to plugins etc... 
> 

It is mostly seamless at this point. But some caveats that I've seen 
recently:

* Some software still doesn't want to work correctly under 64-bit 
environments. Found a bug in GraphicksMagic last year that involved 
certain functionality breaking on 64-bits; Ghostscript was more dicey 
for me (until recently) under 64-bit.

This problem is quickly receding, but certain stuff could still end up 
biting you in the rear.

* 32-bit emulation under Linux sometimes fails. This really only seems 
to be an issue for poorly written commercial software that doesn't have 
a 64-bit version.

Again, this problem is going away, but keep in mind that 64-bit support 
is still not a 100% given.

>   Any good recommendations on Linux compatable mobos?
> Most I have used I never had issues with but not sure
> about 64bit.

For low-end, I've found A64+VIA chipsets to be flawless in all respects 
- everything "just works" out of the box. Our next round of servers will 
be Opteron+Serverworks chipset; not sure what you're building, but that 
isn't an option for the desktop.

I'd stay away from the older PentiumIV based stuff on Intel chipsets - 
it'll work very well, but you may give up performance. Our one Intel 
Xeon box here, 64-bit, was a very simple install, again, under Gentoo. 
Since it is a acting as a file server, CPU isn't really much of an issue.

My $.02

jh


>   Thanks everyone for all you help! 
> 
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