[ILUG] Via C3 chips.

[Padraig Brady]

This might be of interest to you:
http://rura-pentaa.mit.edu/silence/c3/intro.html

John P. Looney wrote:
> On Thu, Feb 28, 2002 at 02:59:06PM +0000, Gavin McCullagh mentioned:
> 
>>Does anyone have experience with linux and these chips?  There's up to
>>933MHz available (at ST£62 inc VAT).  The attraction is it's low power 
>>consumption and in particular capability of running with a passive heatsink.
>>
> 
>  Oh, we've lots of that...
> 
> 
>>* Do I assume as Pentium 3 compatible linux will work seamlessly or is this
>>naive?  Anyone have any links to docs about this?
>>
> 
>  You can compile a kernel with M3 specific stuff - like 3DNOW support
> (speeds up memcpy, stuff like that). Compile all your apps as if it's a
> pentium, and you are away.

C3's don't have CMOV instructions, so they can't run PIII specific code.
The kernel has C3 specific config option. gcc settings should
select i586, not i686 (CMOV is officially optional on 686, but gcc
doesn't make it optional).

> 
> 
>>* I take it gcc doesn't have optimisations for it though, or does it?
>>
> 
>  Not really. Consider it a Pentium with 3DNOW or whatever.
> 
> 
>>* out of interest, anyone have ideas of it's performance
>>
> 
>  It seems to be about 20% slower than a celeron of the same clock speed.
> The FPU is about 40% slower, at a guess. But, we've boxes with M3's in
> them, running at 18 watts, so for low power/no fan stuff, they rock. But
> in a desktop...I'm not sure. They cash saving isn't that great.
>  

These figures were for the previous Samuel II core. The new
ezra is the same or sometimes a little better than the same
speed Celery. FYI here's a table I've compiled detailing VIA chips:
All CPUs are S370 and take about 6-12 Watts

----------------------------------------------------------------------------------------
core 
	size	name		code    Notes
----------------------------------------------------------------------------------------
samuel          0.18µm  Cyrix III       (C5)    (128K L1 0K L2 cache). 
FPU doesn't run @ full clock speed.
samuel II       0.15µm  C3              (C5B)   667MHz CIII in Dabs are 
C3's (128K L1, 64K L2 cache), (MMX/3D now!), FPU @ full clock speed.
mathew          0.15µm  C3              (C5B)   mobile samuel II with 
integrated north bridge & 2D/3D graphics. (1.6v)
ezra            0.15µm  C3              (C5C)   800-1000MHz,Q4 2001 (1.35v)
ezra-T          0.13µm  C3              (C5M)   800-1000MHz, Q1 2002
ezra-T          0.13µm  C3              (C5N)   900-1200MHz, Q2 2002 
(256K L2 cache)
nehemiah        0.13µm  C4              (C5X)   1.1-1.2GHz, Q3 2002 (SSE)
nehemiah        0.13µm  C4              (C5XL)  1.2-1.5GHz, Q4 2002
esther          0.10µm  C4              (C5Y)   > 1.5Ghz, Q3 2003

Padraig.