Re: Note Pentium Optimized only really helps P5 CPUs ...
On Fri, Jul 02, 1999 at 03:06:31PM -0500, Anderson MacKay wrote:
> On Fri, Jul 02, 1999 at 05:51:39AM -0500, R. Brock Lynn wrote:
> > I'd be impressed, as I'm sure a lot of other folks would to at a
> > decision from Debian to add to it's list of offerings, a pentium
> > optimized set of packages.
>
> [NB: this is just a pre-emptive strike before a thousand people jump into
> this thinking that "Pentium optimizations" will speed up their machine a
> lot. I'm just pointing out the architectural restrictions that make the
> Pentium a machine for which optimized code makes a huge difference. If
> this bores you, delete this now and feel no remorse.]
>
> I don't want to throw water on this fire, since the ability to layer
> things architecturally would be a great benefit to Debian. But before
> everyone does the Stampede thing and compiles everything
> Pentium-optimized, be aware that Pentium optimizations only make a big,
> noticeable difference for the original and MMX Intel Pentium (not PPro,
> not P2, not P3, not K6, etc.) processors. The big speedup is because the
> compiler/assembler reschedules integer instructions so that they can
> execute in parallel inside the Pentium's two integer pipelines (which
> have rather primitive inter-pipeline conflict/dependency resolution
> hardware). Most CPUs since then (Cyrix 6x86MX/M2, AMD K6-series, and
> Intel P6-series including PPro, P2, P3, and Celeron) have better conflict
> and dependency analysis/resolution hardware (or can execute
> out-of-order), and don't gain much from Pentium-specific optimizations.
> In fact, most other CPUs run better with plain old i386 or i486 code than
> they do with Pentium-optimized code.
>
> That said, Pentium optimizations *should* really help out owners of the
> genuine Intel Pentium (and MMX) processors. By virtue of the additional
> flexibility for old machines, I'd be impressed to see Debian do this --
> it would probably require resolving some of the same problems that hold
> back a true segmentation of the distribution. So, from an infrastructure
> and making-the-distribution-amazing (as if it isn't already :)
> standpoint, this is a good thing -- from a speeding-up-your CPU
> perspective though, it's only a great thing if you have a true
> made-by-Intel Pentium or Pentium MMX.
I like the idea of having optimized packages for the High-End users
but i think it will cause a LOT bigger ftp sites (EV4 EV5 EV6 -> 3 times
more alpha) (pentium, ppro, k7 -> 3 times bigger i386).
I would more like the idea of "local" compiler options - Means - If i am
able to do "apt-get compile apache" it should use MY compiler
(e.g. pgcc) and the optimizations i would like to have. This optimization
issue is only interesting for "High-End" users and they have some
cpu-cycles left on installation.
---/etc/compilersettings-----
CC=pgcc
CFLAGS=-mpentium
-----------------------------
Flo
--
Florian Lohoff flo@rfc822.org +49-5241-470566
Good, Fast, Cheap: Pick any two (you can't have all three). (RFC 1925)
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