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On Dual-head DVI ViewFinder graphics card announced:

I think the bigger economic interest in solving the incomplete compatibility of RISC OS Six with ViewFinder lies with ROL. ViewFinder is not back in production, and there's a very limited number of upgrades. Once these are gone, it's sort of back to blissful anonymity. Dual-head DVI is mainly something I wanted myself, and since I'm probably not the only one, I decided to make it available.

 is a RISC OS Userjk on 27/8/09 12:05AM
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On Dual-head DVI ViewFinder graphics card announced:

Practically all of the differences between AGP cards of the same class (Mach 64, Rage 128, Radeon) are in their initialisation. This is probably still done by the ViewFinder firmware before RISC OS 6 silences it. The RISC OS 6 driver for ViewFinder, therefore, hardly needs to deal with differences between AGP cards of the same class. Mostly only with acceleration. And even between classes, there are very few differences in implementing acceleration.

 is a RISC OS Userjk on 24/8/09 3:40PM
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On Dual-head DVI ViewFinder graphics card announced:

On a Risc PC running RISC OS 4.39 and a Radeon ViewFinder it is between 1200 and 1500 MB/sec.

 is a RISC OS Userjk on 20/8/09 10:40PM
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On Dual-head DVI ViewFinder graphics card announced:

I do have a fillrate test, here :

[link]

This will give a good idea of the general speed of rectangular drawing operations, which are by far the most important in the desktop.

 is a RISC OS Userjk on 20/8/09 8:45PM
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On Dual-head DVI ViewFinder graphics card announced:

The podule bus is only the bottleneck for operations that hardly benefit from acceleration in the first place (e.g. line drawing). These operations have little or no impact on overall desktop performance.

If you would expend the effort to make them as fast as possible anyway, it's simply a matter of limiting the amount of data going across the podule bus. There's no difference in potential for that between ATI chipsets and SM50X. Their programming models are virtually identical.

 is a RISC OS Userjk on 19/8/09 11:36PM
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On Dual-head DVI ViewFinder graphics card announced:

You don't realise exactly how acceleration works.

It involves sending a parmeterised command to a drawing engine, which then does the drawing all by itself. The podule bus is only involved in the transfer of the command (which is, say, 8 words long). I.e. the drawing speed is completely dominated by the memory bandwidth available to the drawing engine (e.g. 1.2 GB/sec in Radeon's case), not by the bandwidth of the podule bus (8 MB/sec with DMA).

This is true for all drawing operations that benfit most from acceleration, i.e. where the drawing engine draws a lot of pixels, like rectangle copy (used for moving windows around the desktop) and rectangle fill (used for clearing window and menu backgrounds). In ViewFinder's case, since it caches sprites in the video card's memory as well, it even applies to sprite plotting (if the sprite data was not cached, it would have to pass the podule bus on each draw).

 is a RISC OS Userjk on 19/8/09 1:55PM
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On Dual-head DVI ViewFinder graphics card announced:

I don't know where this nonsense about acceleration performance comes from.

Radeon has a memory bandwidth of 1.2 GB/sec. SM501 has half that. Both have similar command overheads and both are behind the podule bus. So unless the ViewFinder driver of RISC OS 6 is absolutely shoddy compared to the VPod's (and even not then, since for operations where acceleration is most relevant, overhead is least so), ViewFinder will generally be much faster than VPod.

 is a RISC OS Userjk on 19/8/09 12:55PM
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