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- Posted on
April 13, 2011, 2:32 pm
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I'm wondering if there is now a software method of employing multiple
(older PCI and or AGP) video cards to output to a single monitor having
shared processing work (as in the old 3dFX cards or the current Sli/CF
Does this sound reasonable or would it be impossible to implement??
Re: AGP, standard PCI video cards: daisy chaining/SLi/Crossfire?
There was an attempt.
On the older 3DFX setups, they used analog (VGA) overlay.
The 2D video card sent its VGA signal to the 3DFX card, and
the 3DFX sync'ed to the video the 2D card was delivering.
The scan line interlacing was done by the SLI cable. The "master"
card, is the one in the middle, and it combines the digital
output of both 3DFX cards, then analog overlays then on top
of the 2D signal. You should be able to do windowed or full
screen that way, without glitching the sync to the monitor.
Modern graphics cards tend to integrate both 2D and 3D features,
so they don't use the analog overlay method any more.
I would say, theoretically, you could combine the computations
of a few cards. But practically, the software is missing to do that.
The PCI bus, in particular, is a poor choice, due to the limited
bandwidth. If you attempted to exchange large pixmaps between
cards, the bus would be saturated. AGP on the other hand, has
good bandwidth (up to 2.1GB/sec), but you only get one slot
A better candidate, might be a computer with PCI66/64 slots. The
only cards I know of, with interfaces like that, are Matrox. And
I don't know if Matrox would support combining card output. Matrox
are typically selected for applications such as stock trading and
driving perhaps four monitors from one card.
About the best you could do, is to buy a video card with a
modern PCI Express GPU and a bridge chip to interface to AGP.
NVidia had "HSI" and ATI had its "Rialto" bridge. NVidia stopped
making their AGP (bridged) cards, when they could no longer
manufacturer the bridge chip. Rialto lasted a bit longer, but
I don't think ATI really liked the amount of effort to write
drivers for their products. They tried to limit the effort
put into those drivers.
This card fits in your AGP slot, and uses a Rialto on the back.
The pink protective material, prevents SMT components on Rialto
from being scraped off.
You can see what the pink stuff covers up, in this photo.
Before purchasing, you have to check the customer feedback entries,
to see whether the drivers work and can be installed. There are
generally lots of driver issues, and you have to obtain proof from
a previous owner, that a stable software configuration exists, before
you buy one.
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