Quotes
“While there is a lot of good documentation on the Emotion Engine, much less is known about the Graphics Synthesizer (GS) and thus while the ‘what’ of the discussion should be accurate, the ‘why’ may not.
In terms of quality features and functional complexity, the GS is very much like an extremely fast 3dfx Voodoo Graphics chipset. Although Sony has 32-bit color, 32-bit Z-buffer support, the GS only has the standard OpenGL/D3D texture blend modes, leaving out the new features such as DOT3 or EMBM bump mapping, cube reflection maps, or texture compression.
As mentioned in the specifications page, the Graphics Synthesizer has 16-pixel pipelines running at 150MHz with 32-bit color, 32-bit Z-buffer. While we would expect this to mean a fill rate of 2.4 gigapixels/sec, Sony's press release indicates that texturing cuts the fill rate in half to 1.2 gigapixels/sec. This suggests that the GS requires a full clock cycle to get the texels.”
Thus, when multitexturing, the fill rate should drop to 600Mpixels/sec. This should put the PlayStation 2 somewhere between the GeForce DDR and GeForce2 GTS. Though the 640x480 target resolution needs to be taken into account, the GS is really underpowered when compared to the X-box's claimed specs. The Dreamcast only has a raw fill rate of 100Mpixels/sec, but again the deferred rendering takes this value effectively up anywhere from 200Mpixels to even 1 gigapixel/sec.
Since the details aren't clear, it's hard to make a definite call but we suspect the answer is "no." The PS2 has a 2560-bit interface to the embedded DRAM at 150MHz. This equals a total of 48 GB/s, and yes, it is an incredible amount of bandwidth. However, only 512-bits are available for texture lookups which leaves 9.6 GB/s. The GeForce2 GTS has 166MHz DDR on a 128-bit interface which equals 5.312 GB/s.
The difference is that PS2 has to provide texture information for 16 pixels each clock cycle whereas the GTS only needs to provide texture information for 4 pixels. So, for each pixel, the GTS has 1328 MB/s of bandwidth whereas the PS2 only has 600 MB/s of bandwidth for retrieving textures. The Dreamcast has 800MB/s for each pixel. If you factor in texture compression, you need to multiply the Dreamcast's and GTS's numbers by 4. In other words, although there is more total bandwidth for the PS2, it also needs more bandwidth to reach its theoretical maximum because of its massively parallel design.
Granted, once the textures information has been provided, there is 2048-bits of read/write bandwidth for the frame buffer giving 38.4 GB/s of bandwidth. Unfortunately, there are still two lingering concerns. 16-pixel pipelines instead could ruin efficiency. Conventional 3D chips render one polygon at a time.
If you have a 1x1 polygon, then only 1 pixel pipeline could be used and 15 will sit idle, just wasting throughput. The GeForce, for example, has its four pixel pipelines in a 2x2 array. At the corners of polygons, the four pixel pipelines are rarely all used. The only way around this would be for Sony to use something completely different from PC graphics chips and "unhook" the pixel pipelines, but there is nothing to suggest that this has been done. Smaller polygons will result in poorer performance.
Unfortunately, the use of a lot of small polygons is exactly what the Emotion Engine affords. In addition, texture bandwidth is likely to be extremely important because the PS2 only has 4MB of embedded DRAM.”
In terms of quality features and functional complexity, the GS is very much like an extremely fast 3dfx Voodoo Graphics chipset. Although Sony has 32-bit color, 32-bit Z-buffer support, the GS only has the standard OpenGL/D3D texture blend modes, leaving out the new features such as DOT3 or EMBM bump mapping, cube reflection maps, or texture compression.
As mentioned in the specifications page, the Graphics Synthesizer has 16-pixel pipelines running at 150MHz with 32-bit color, 32-bit Z-buffer. While we would expect this to mean a fill rate of 2.4 gigapixels/sec, Sony's press release indicates that texturing cuts the fill rate in half to 1.2 gigapixels/sec. This suggests that the GS requires a full clock cycle to get the texels.”
Thus, when multitexturing, the fill rate should drop to 600Mpixels/sec. This should put the PlayStation 2 somewhere between the GeForce DDR and GeForce2 GTS. Though the 640x480 target resolution needs to be taken into account, the GS is really underpowered when compared to the X-box's claimed specs. The Dreamcast only has a raw fill rate of 100Mpixels/sec, but again the deferred rendering takes this value effectively up anywhere from 200Mpixels to even 1 gigapixel/sec.
Since the details aren't clear, it's hard to make a definite call but we suspect the answer is "no." The PS2 has a 2560-bit interface to the embedded DRAM at 150MHz. This equals a total of 48 GB/s, and yes, it is an incredible amount of bandwidth. However, only 512-bits are available for texture lookups which leaves 9.6 GB/s. The GeForce2 GTS has 166MHz DDR on a 128-bit interface which equals 5.312 GB/s.
The difference is that PS2 has to provide texture information for 16 pixels each clock cycle whereas the GTS only needs to provide texture information for 4 pixels. So, for each pixel, the GTS has 1328 MB/s of bandwidth whereas the PS2 only has 600 MB/s of bandwidth for retrieving textures. The Dreamcast has 800MB/s for each pixel. If you factor in texture compression, you need to multiply the Dreamcast's and GTS's numbers by 4. In other words, although there is more total bandwidth for the PS2, it also needs more bandwidth to reach its theoretical maximum because of its massively parallel design.
Granted, once the textures information has been provided, there is 2048-bits of read/write bandwidth for the frame buffer giving 38.4 GB/s of bandwidth. Unfortunately, there are still two lingering concerns. 16-pixel pipelines instead could ruin efficiency. Conventional 3D chips render one polygon at a time.
If you have a 1x1 polygon, then only 1 pixel pipeline could be used and 15 will sit idle, just wasting throughput. The GeForce, for example, has its four pixel pipelines in a 2x2 array. At the corners of polygons, the four pixel pipelines are rarely all used. The only way around this would be for Sony to use something completely different from PC graphics chips and "unhook" the pixel pipelines, but there is nothing to suggest that this has been done. Smaller polygons will result in poorer performance.
Unfortunately, the use of a lot of small polygons is exactly what the Emotion Engine affords. In addition, texture bandwidth is likely to be extremely important because the PS2 only has 4MB of embedded DRAM.”
posted by Phenom at 10:52 AM
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