[Virtualacorn-list] VirtualRPC Speed Comparisons...

[Alan Adams]

In message <gemini.k8in4x000xoox04h8.pittdj at pittdj.co.uk>
          David Pitt <pittdj at pittdj.co.uk> wrote:

> Roger Darlington <rogerarm at freeuk.com> wrote:

>> On 10 Oct 2008, David Pitt wrote:
> [snip]
>>> 
>>> The significance is that it would explain the speed difference, Geminus
>>> is a video accelerator that does work on jpegs.
>> 
>> And that alone would explain the six-fold difference in speed? WOW!

> I suppose it has to, I cannot think of anything else that might be different
> between our Iyonixes. The only way to prove it is to remove or disable
> Geminus, there may be a *command for that. When I first installed Geminus
> here I remember being impressed.

Are you using the same image? The degree of compression in a JPEG file 
is variable, so two files of the same original size could end up with 
a pixel size of 2 to 1. This would go a significant way to explaining 
such a speed difference.

>> But x86 computers also have (extremely powerful) graphics cards that VRPC
>> presumably has access to, so I would still be looking for a speed increase
>> of VRPC over a Geminused Iyonix of more than double (with respect to
>> !Variations).

There was an attempt some years ago to use the floating point 
coprocessor of a PC card in a RiscPC to improve floating point speed. 
The results were not good - the overhead of trapping the operation, 
passing it to the coprocessor, and retrieving the results outweighed 
the faster execution in most cases.

VRPC would not be as bad, because the emulator and the coprocessor are 
closer to each other, i.e. both in the PC, rather than one being in 
the RPC and the other in a plug-in card. That could help.

> The Iyonix has an NVidia GeForce FX5200 and the laptop  has an NVidia
> GeForce 8600M GT.

> My Toshiba Qosmio G40 laptop has been superseded by faster, and cheaper,
> variants, VRPC could be truly nifty on one of those, but to be fair it is
> pretty good in speed terms on this one.



-- 
Alan Adams, from Northamptonshire
alan at adamshome.org.uk
http://www.nckc.org.uk/