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[PS3Scene]

SCEA Releases PS3 Deferred Shading and Rendering FAQ Posted by XanTium | 12-9-2007 0:14 EST

From gamers-creed.co: This paper studies a deferred pixel shading algorithm implemented on a Cell-based computer entertainment system. The pixel shader runs on the Synergistic Processing Units (SPUs) of the Cell and works concurrently with the GPU to render images. The system's unified memory architecture allows the Cell and GPU to exchange data through shared textures. The SPUs use the Cell DMA list capability to gather irregular fine-grained fragments of texture data generated by the GPU. They return resultant shadow textures the same way. The shading computation ran at up to 85 Hz at HDTV 720p resolution on 5 SPUs and generated 30.72 gigaops of performance. This is comparable to the performance of the algorithm running on a state of the art high end GPU. These results indicate that a hybrid solution in which the Cell and GPU work together can produce higher performance than either device working alone. Download: research.scea.com News-Source: gamers-creed.co

[mik30]

Interesting is especially the following paragraph:

"D. Comparison to GeForce 7800 GTX GPU
We implemented the same algorithm on a high end state of
the art GPU, the NVIDIA GeForce 7800 GTX running in a
Linux workstation. This GPU has 24 fragment shader
pipelines running at 430 Mhz and processes 24 fragments
in parallel. By comparison the 5 SPEs that we used process
20 pixels in parallel in quad-SIMD form.
The GeForce required 11.1 ms to complete the shading
operation. In comparison the Cell/B.E. required 11.65 ms."

This result is embarassing for Sony.
In spite of all the effort to parallelize the shading process
the PS3 is slower than a 7800 GTX, which is in fact an
obsolete product and nowadays by no means
"state of the art" or even "high end"...

To publish these results is actually rediculous if Sony
wants to underline the power of the PS3 architecture.
On the other hand anybody has now a proper explaination
why the PS3 is so often slower than the 360.

[anonim1979]

You don't get it.

RSX is weak and all kind of help from Cell is welcome
GPU in PS3 is only slightly upgraded midrange GF7600GT taken from PC at the last moment when it came to light that projected 2xCell PS3 with no GPU would mighty su*** compared to X360.
128bit 8ROP 500Mhz 256MB DDR3.
Only pixel shaders were doubled from 12 to 24.

And as can be seen Cell is VERY capable of helping RSX in some operations.
No more framerate issues in properly written PS3 games I hope.

[mik30]

QUOTE(anonim1979 @ Sep 12 2007, 02:44 PM)

You don't get it.

RSX is weak and all kind of help from Cell is welcome
GPU in PS3 is only slightly upgraded midrange GF7600GT taken from PC at the last moment when it came to light that projected 2xCell PS3 with no GPU would mighty su*** compared to X360.
128bit 8ROP 500Mhz 256MB DDR3.
Only pixel shaders were doubled from 12 to 24.

And as can be seen Cell is VERY capable of helping RSX in some operations.
No more framerate issues in properly written PS3 games I hope.

Well, I do get everything but You do not get what I wrote:
According to the results the GFX power of the PS3 is even
with SPE support, which is actually not used to day, slower
than a GF7800 GTX. The 7800 is an obsolete GFX chip
and by no means "high end" or even state of "the art".

BTW:
Besides my 360 & PS3 I own a P4 3.2GHz PC with a
GForce 6800GT which is almost identical to a 7800 in terms
of speed.  I can tell you that the 360 is in terms of grafical
speed MUCH more powerfull when comparing identical
games. So in accordance to this article that fits quite well
to the poor performnce most ported games deliver on the PS3.

One has to remember that the PS3 is still hyped as a grafical
"speed king" and is still denoted as a "supercomputer" regarding
its computational power. According to Sony´s promises before
the release every game should run at 60FPS in 1080p. The reality
now is far from that. That was obviously just Sony marketing
regarding the published results.

[epsilon72]

^There is a noticeable difference between the 6800 and the 7800 - look for the blue bars.

[Swahili]

This is the one you want

http://www23.tomshardware.com/graphics_200...4&chart=318


I'm pretty sure that with the help of the cell, any game can look better on the ps3. But they won't, since it takes time to code for the cell and multiplatt titles won't afford the time taken to do so. Therefor I'm quite happy with my 360 so far. Just a shame it doesn't emulate the much better and richer playstation library instead of the old xbox1 (IMG:style_emoticons/default/smile.gif) ...

This post has been edited by Swahili: Sep 12 2007, 05:04 PM

[d-range]

QUOTE(mik30 @ Sep 12 2007, 04:55 PM)

Well, I do get everything but You do not get what I wrote:
According to the results the GFX power of the PS3 is even
with SPE support, which is actually not used to day, slower
than a GF7800 GTX. The 7800 is an obsolete GFX chip
and by no means "high end" or even state of "the art".

Offloading to the SPE's frees up the GPU so it has to do less. If it has to do less, stuff runs faster. It's as simple as that. If you throw all your graphics processing at the GPU you choke it (because in the PS3 it's indeed pretty low-spec), and it becomes a bottleneck for the rest of your code. The SPE's are autonomous units, if they would be idle otherwise, any processing you offload to them you get almost for free.

As for the 1-1 performance comparison: this particular program might perform just 'on par' with a low-spec GPU, but that says nothing about the potential of the SPE's. There might be (in fact: there *are*) other graphics-processing algorithms that you could easily implement on a GPU (like you would on a 360), but which would perform much better on the SPE's. They're different (though somewhat comparable) architectures, and they excel at different applications.