64-bit RPM/APT based systems - Worth it?

[Jerry Feldman]

On Sun, 30 Oct 2005 09:27:13 -0500
Bill McGonigle <bill at bfccomputing.com> wrote:

> On Oct 29, 2005, at 20:24, Brian Chabot wrote:
> 
> > How backward-compatible are they with 32-bit apps?  I know there would
> > be a certain lossin performance, but for instance, would a commercial
> > version of UT2004 for Linux be able to run on a 64-bit system?
> 
> Someone will correct me if I'm mistaken, but as I understand it x86-64 
> is an instruction set addition to IA32.  So it's not a 64-bit chip like 
> an Alpha, it's a 64-bit chip like a PowerPC. A fundamentally 32-bit 
> chip with provisions for 64-bit operations and memory addressing.
> 
> So, AFAIK, you can run a 32-bit distro just fine on them (unlike 
> Itanium) which will leave some of the silicon idle, but when a 
> compelling 64-bit OS comes out you're good to go.
Yes to some extent. There are several modes of operation:
A 64-bit OS
	32-bit apps
	64-bit apps
A 32-bitOS
	32-bit apps only.

There are more registers and in 64-bit mode, each register is 64-bits
wide. (I have the Opteron architecture manual at work).

In 32-bit mode, you will be using the 32-bit instructions set and
memory architecture.  Currently the AMD chip is the better of the 2
x86-64 chips. The Intel EM64T lags a bit behind, and they just
canceled their Xeon with Whitefield technology. Apparently Intel's
Bangalore operations really dropped the ball. The big benefit of the
x86-64 architecture is the linear memory model and the additional
registers that are not available in 32-bits. 
-- 
Jerry Feldman <gaf at blu.org>
Boston Linux and Unix user group
http://www.blu.org PGP key id:C5061EA9
PGP Key fingerprint:053C 73EC 3AC1 5C44 3E14 9245 FB00 3ED5 C506 1EA9
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