nVidia's Xbox chip..

Soccerman

Elite Member
Oct 9, 1999
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Well it appears that I and many others on this forum were correct, in that nVidia will attempt to skirt the issue of memory bottlenecks with a tile renderer.

"There's also occlusion-detection circuitry that can increase fill rate by up to 4X; the effect varies depending on whether pixels are occluded when they're drawn, but tends to be greatest exactly when it's needed most -- when there's a lot of overdraw" is the exact wording. occlusion meaning, blocking detection.

I'm not surprised, neither should you be. in any case, it's only a stop gap measure, many more methods need to be used to reduce memory bandwidth dependancy, as I'm sure they have been working on.

This is what surprises me right here.. "The GPU's raw fill rate at 250 MHz will be 1 Gpix/sec."

WTF? so now they have 4 pipes STILL, and possibly 2 or more texture units per pipe. that's not that impressive IMHO, it's just a Geforce 2 with a few more mhz (50 to be exact) and tile based rendering.

Though I wouldn't be surprised if they put 3 texture units per pipe, that doesn't matter too much to me, becuase the emphasis SHOULD be increasing polygons, rather then increasing layers of textures. (I consider 3 or 4 the max amount for Bump Mapping etc)

here's the link BTW, thanks to NFS4 http://www.ddj.com/articles/2000/0008/0008a/0008a.htm

EDIT-Included more text from the article in a quote.
 

KarlHungus

Senior member
Nov 16, 1999
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While they seem to be using some techniques common on tile renderers it does not appear to be a true tile rendering scheme.

Also, who cares how many pipes they have? Assuming the same architecture that they have (running at 250MHz), plus the occlusion-detection circutry, they have a maximum effective fillrate of 8 GTex/s (in the best case senario).

If anything the Kyro has shown us that this technology works quite well, and I'm looking forward to nVidia's implementation.
 

Soccerman

Elite Member
Oct 9, 1999
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there's no question it's evolutionary, it's faster.. because it avoides the memory bottleneck a fair amount. I was expecting something.. well more revolutionary. Something we hadn't thought of. more features, IE hardware Voxel renderer.. something new!

oh well, at least it'll make the current video cards alot less expensive!

take a look at this "It is with this sort of rendering that Xbox will really shine: Think of the droid army in The Phantom Menace"

yikes, remember the people at Pixar and their response to a similar comment about nVidia products?

"That leaves one potential bottleneck, and it's a big one -- memory bandwidth. Xbox has a unified memory architecture (UMA), whereby the GPU and CPU share a single memory space, with memory control provided by the GPU."

hmm, doesn't sound that great, though the 'GPU' probably is the most needy of Bandwidth..
 

KarlHungus

Senior member
Nov 16, 1999
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Well, they haven't released the full specifications yet, so there's still hope!

Ditto on that last comment. ;)
 

Bloodybrain

Member
Oct 11, 1999
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The Xbox is going to be used with a low-resolution TV screen. No need for QDR memory when you've got a 512x384 display to fill.