[vorbis] Minimum cpu requirements

[Maik Merten]

Kerry wrote:
> Anyone know if this would be enough to decode oggs?
> 
> AMD Elan SC520 133 MHz
> 
> If not, what seems to be the lower  limit required for decoding oggs?

Some time ago I did some testings on an underclocked(!) Pentium classic 
@ 50 MHz (Win95, Winamp 2.7x, Peter's RC2 Plugin). This machine was able 
to decode ~96-112 kpbs RC2 files in realtime including streaming the PCM 
data to an old ISA MAD16 soundcard.   All IDE-drives were in slow PIO mode.

The Elan SC520 is based on AMD's 5x86, a 486 "on steroids". The 5x86 @ 
133 MHz performs, roughly speaking, like a Pentium 75 on "real life" 
Windows-software (the 5x86 @ 133 MHz is therefore often called "5x86 
PR75 133). It surely is able to to MP3 decoding in realtime:

"This version plays a layer3,112Kbit/s,J-Stereo stream on my AMD 
5x86/133Mhz with about 66% CPU load. (on the console, NO X11)" (taken 
from mpg123-0.59r README)

Keep in mind that mpg123 is quite optimized. AFAIK Vorbis decoding still 
is a bit slower. Bit-rate "spikes" could be critical.

The Elan SC520 has quite a small L1 Cache (16 KB) without a L2-Cache (I 
think there's no L2-cache controller in SC520). Of course, the 
integrated SDRAM-controller should be faster than those 486 FPM Chipsets 
  - so the missing L2-Cache should not have a too big impact on 
memory-performance. Well, to be honest, I'm guessing here.

By the way: The predecessor of NS Geode, the Cyrix MediaGX, also was 
based on a 486-like core (a Cyrix 5x86 - roughly the same performance as 
AMD 5x86). The MediaGX had integrated VGA (UMA), Sound, PCI etc...
The very FPU-demanding Quake did run (roughly speaking) with Pentium 60 
performance on a MediaGX @ 133 MHz. I do expect similiar results for the 
AMD 5x86/Elan SC520.

<p><p>> Many thanks,
> Kerry.

bye,

Maik Merten

<p>--- >8 ----
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