Re: AW: AW: Creating a planetarium using Ruby

[Helge H. <hel...@ai...>]

Unger Richard wrote:

>Hi!
>
>I don't really know, because I have not tried, but I think the problem with smooth Animation across 20 Screens in one PC is the bus speed. 
>
>The PCI bus can transport 127MB / sec.
>  
>
If it is a 32-bit 33MHz bus.  (133 MB/s, but some is lost to overhead.)
There are also the more expensive 64-bit 66MHz bus, that gives you
4 times as much, 533MB/s minus overhead.

>Lets assume you run each screen at 1024x768, 16 bit = 1,5MB / screen
>Now 20 Screens is 30MB of data, 127MB/30MB ~ 4, ie you could (theoretically) drive the screens at 4 fps.
>
>That's not exactly smooth animation.
>  
>
Sure not.  One could display nice very high resolution images though. :-)
But throw in a server board with two of those 64-bit buses, and you
could hit 32 fps in theory.  Well, if you can find dual or triple screen
cards for 64-bit pci that is. Gamers might not be impressed with 32 fps,
but it beats movies at least.

Some cards have mpeg decoders on them - this will allow large bandwith
savings when playing prearranged video/animations.  I am not sure mpeg
for 20 screens could be generated in realtime.

>Now I freely admit that calculation is simplistic. In a modern computer some of the screens would be connected to an AGP bus, some could be connected to PCIe. Some boards might include more than one PCI bus, meaning the cards don't all have to share the 127MB...
>
>Still, until I actually tried it out, I would be worried about trying to move that amount of data (all screens more or less in sync!) on Pc-type hardware...
>  
>
No guarantee that one gets near the theoretical limit. :-/
The synchronization should be simple, just take care to
update the screens in sequence.


Helge Hafting