[mythtv-users] Performance from a different perspective

[Paul V. Gratz]

On Tuesday 24 January 2006 12:14 pm, Raphael Pooser wrote:
> Well Cache is important.  Another reason a Celeron will suck compared to 
> a P4 is the bandwidth between the processor and RAM is crippled.  The 
> Celeron front side bus was always chopped in half compared to a 
> pentium.  The netburst architecture has always been bandwidth hungry, so 
> you take a netburst chip, hack off 75% of it's cache and crack it's FSB 
> to pieces, and yeah, it ain't gonna do much compared to a P4.  I don't 
> know much about HD, but from a gaming POV, a #GHz celeron is like a 
> 1.8-2.0GHz P4.  Basically the general rule avoid celerons like the 
> plague for all tasks except email and word processing applies to HTPCs 
> too I would think.
> In reality, encoding/decoding is computationally intensive, and at the 
> same time you need bandwidth as these actions involve streaming.  since 
> Celeron is piss poor at floating point and has no bandwidth to access 
> the RAM, it must suck for HD on HTPCs.  However, if anyone is using one 
> successfully I'd like to know.
> Disclaimer: this email written by someone extremely hostile to intel 
> smellerons.


Actually I have to completely disagree. For encoding and decoding
applications caching is not very important.  A cache only helps when
you have spacial or temporal locality, video and audio encoding do not
have temporal locality and the spacial locality is small, small enough
for a small cache.  In this sort of application you are streaming data
in, performing some operations on it and streaming it back out never
to be seen again (at the time scale a processor runs at).

Also this is the sort of application that intel's highly pipelined
architecture excels at, heavy on the math and very predictable
branches.  By contrast, AMD's architecture has a shorter pipeline and
therefore does not suffer as much on branch mis-predicts, this means
its much better at code like the Spec Int benchmarks (think gcc
compilation, perl and Java JITs, game AI and that sort of thing).

The only thing that might be hurting the Celeron D vs the P4 is the
relatively lower FSB speed, however my gut feel is that video, even HD
TV, does not really stress the FSB.  It probably is a higher stress on
the PCIx/AGP busses (I could work the math but I'm feeling lazy,
anyone want to chime in?)

Incidentally here is a set of benchmarks Anandtech did when the
Celeron D came out a year or so ago that back up what I say:

http://www.anandtech.com/printarticle.aspx?i=2093

Paul

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