View Full Version : Does Ps3 need RSX or can Cell do his work?
MrCarrefour
22-Aug-2009, 09:06
Hi, I was just wondering if a Cell processor should do the RSX chip work.
If it's impossible, why?
Wondering about a Ps3 with a PoweCell or with more than one Cell processor, what's about a Ps3 missing a GPU?
(my question is just for wondering) :wink:
Texturing and rasterization (i.e. figuring out the pixel area that is covered by a triangle) have traditionally been much more efficient on dedicated hardware. That, and very fast depth and stencil handling, are the big advantages of dedicated GPUs.
I think CBE@3.2GHz has a slight (~25%) theoretical advantage over RSX when it comes to shader throughput, but that's only one item on a long list of things a GPU needs to do.
Cell alone could not come close to delivering the games we have on PS3 currently.
A machine with two CBEs might be in a roughly similar performance ballpark, although most likely still below the current PS3 setup. And that's the theory where all hardware is utilized efficiently.
In practice, the level of abstraction offered by GPUs is well understood and much more comfortable to work with than a pool of SPEs rendering triangles. That's an extra strike against software rendering.
Mike Acton
22-Aug-2009, 16:14
The Cell isn't really going to beat the RSX at its own game. As Rolf N said, dedicated h/w is good at what it does. However, it gets in to a gray area when you start talking about other things, like more complex post processing (e.g. building sum tables).
To answer your question - It's not "impossible" for the Cell to do the work of the RSX. It's just not a very good use of the h/w.
There *is* another side to the story though - if you start talking about rendering that's not based on triangle rasterization, then you open up the door for the Cell. e.g. ray-tracing. But again, you don't exactly want the rsx just sitting idle, either.
An interesting experiment for someone might be to try and use the RSX as GPGPU and the SPUs for rendering via ray-tracing or something different. Or some other weirder mix. :)
Mike.
Shifty Geezer
22-Aug-2009, 16:18
I'm sure once upon a time some super geniuses would try this sort of thing at University just for a laugh. It's a shame PS3 hasn't attracted these people. What's the best a Lunx renderer is managing at the moment?
Just for laughts and my layman curiosity as well, how would it perform in voxel rendering if the original plans of sony had come to reality with 2 cells instead of the cell+rsx, lets say, if it had 512MB for each cell instead of 256 :lol:
upnorthsox
23-Aug-2009, 01:08
The Cell isn't really going to beat the RSX at its own game. As Rolf N said, dedicated h/w is good at what it does. However, it gets in to a gray area when you start talking about other things, like more complex post processing (e.g. building sum tables).
To answer your question - It's not "impossible" for the Cell to do the work of the RSX. It's just not a very good use of the h/w.
There *is* another side to the story though - if you start talking about rendering that's not based on triangle rasterization, then you open up the door for the Cell. e.g. ray-tracing. But again, you don't exactly want the rsx just sitting idle, either.
An interesting experiment for someone might be to try and use the RSX as GPGPU and the SPUs for rendering via ray-tracing or something different. Or some other weirder mix. :)
Mike.
Mike - Do you feel there's enough flexibility to the RSX to run as a GPGPU and not just GPGPU-ish?
There *is* another side to the story though - if you start talking about rendering that's not based on triangle rasterization, then you open up the door for the Cell. e.g. ray-tracing. But again, you don't exactly want the rsx just sitting idle, either.
The op actually suggests replacing the RSX with a Cell like device, compare the rumors of that Sony originally considered the PS3 to have two Cells and no RSX.
So you'd not have to worry about the RSX sitting idle in this scenario. ;)
noNchaoTic
24-Aug-2009, 08:58
As Mike says, you're never going to beat it at it's own game (rasterization), but I've had great success using it to suplement the processing activities of the RSX. The title I'm currently working on actually does the vast majority of lighting on the SPUs in parallel with the RSX rendering independent views, which I certainly do not consider to be a poor use of the hardware :).
I'm sure once upon a time some super geniuses would try this sort of thing at University just for a laugh. It's a shame PS3 hasn't attracted these people.
yes Ive spoken about this before, ppls/populaces attention spans are becoming shorter + shorter, I shudder to think what it will be like in 50years, prolly exactly like portreyed in some sci-fi dystopia's,
WRT cell specific I know Im disappointed about this, ppl could be doing amazing stuff with it, yet noones really trying
As Mike says, you're never going to beat it at it's own game (rasterization), but I've had great success using it to suplement the processing activities of the RSX. The title I'm currently working on actually does the vast majority of lighting on the SPUs in parallel with the RSX rendering independent views, which I certainly do not consider to be a poor use of the hardware :).
I'd love to hear more about that whenever you're ready to share. ;) Maybe even do a small feature on it for our new Beyond3d podcast. Just let us know if / when you're interested / able to (project may well be under wraps at this point, I imagine).
It doesn't happen to be Hustle Kings, does it? I'm so looking forward to that game. :)
Shifty Geezer
24-Aug-2009, 10:31
Hustle Kings is a good example of a title Cell should excel at. It's dead-simple CSG primitives, meaning a realtime raytracer would be a perfect fit. So far though I haven't seen proper reflections which I was expecting from a snooker/pool title.
noNchaoTic
24-Aug-2009, 11:34
I'd love to hear more about that whenever you're ready to share. ;) Maybe even do a small feature on it for our new Beyond3d podcast. Just let us know if / when you're interested / able to (project may well be under wraps at this point, I imagine).
It doesn't happen to be Hustle Kings, does it? I'm so looking forward to that game. :)
Hi Arwin,
If you PM your email address I will try to set something up :)
Cheers
Cool! I would have sent you a PM already, but I can't yet. You probably need five more posts of something inane like that. ;) But no problem, I created a temporary address on my own domain, go ahead and mail me at ... (done).
Thanks!
Arwin
Panajev2001a
28-Aug-2009, 11:43
The Cell isn't really going to beat the RSX at its own game. As Rolf N said, dedicated h/w is good at what it does. However, it gets in to a gray area when you start talking about other things, like more complex post processing (e.g. building sum tables).
To answer your question - It's not "impossible" for the Cell to do the work of the RSX. It's just not a very good use of the h/w.
There *is* another side to the story though - if you start talking about rendering that's not based on triangle rasterization, then you open up the door for the Cell. e.g. ray-tracing. But again, you don't exactly want the rsx just sitting idle, either.
An interesting experiment for someone might be to try and use the RSX as GPGPU and the SPUs for rendering via ray-tracing or something different. Or some other weirder mix. :)
Mike.
Well, you must like DICE's idea of doing low res rasterization on the SPU's (latest SIGGRAPH paper about Frostbite 2.0) though being a SPU lover yourself :).
IIRC..there's another PS3 game (that came out a long time ago..) that does exactly the same thing.
Err.... Heavenly ? Or Uncharted ?
Panajev2001a
03-Sep-2009, 09:39
No :)
Star Wars? (not that's not ancient)
Resistance?
Crap, this can go on for some time. Any clue ?
The op actually suggests replacing the RSX with a Cell like device, compare the rumors of that Sony originally considered the PS3 to have two Cells and no RSX.
So you'd not have to worry about the RSX sitting idle in this scenario. ;)Well, there where alot of patents and shematics floating around at that time. Using a Cell like its known as GPU is a bad idea (and certainly never was considered), but I remember schemes that had a Cell with SPUs and rasterizer-elements hanging on the EIB.
This would`ve been an interesting pairing, SPUs could do the Vertex-work and the Pixels are done in dedicated hardware.
Lucid_Dreamer
04-Sep-2009, 15:48
Well, there where alot of patents and shematics floating around at that time. Using a Cell like its known as GPU is a bad idea (and certainly never was considered), but I remember schemes that had a Cell with SPUs and rasterizer-elements hanging on the EIB.
This would`ve been an interesting pairing, SPUs could do the Vertex-work and the Pixels are done in dedicated hardware.
It kind of sounds like the current pairing. Just replace your words "dedicated hardware" with the term RSX. :)
It kind of sounds like the current pairing. Just replace your words "dedicated hardware" with the term RSX. :)Well, the difference would be that those SPUs and "PixelUnits" would sit on the same chip and could pass data back and forth at insane speeds instead of using an external Bus. Also there would be no vertex-shaders.
If thats the same for you, then Fusion/Larabee is the same as a CPU + seperate GPU aswell.
Lucid_Dreamer
05-Sep-2009, 13:30
Of course, that would mean less vertex work could be done in favor of faster pixel work. I'm glad you were more specific this time. :wink:
green.pixel
06-Sep-2009, 17:52
I Have a question. Why exactly was the original 2xCell design abandoned, if such an idea ever existed in the first place? Sure, the development would be much more painful, and budget for implementing 2xCBE compared to RSX would be much higher?
Sorry, I wasn't following exactly from the start of the generation.
Panajev2001a
06-Sep-2009, 18:01
I Have a question. Why exactly was the original 2xCell design abandoned, if such an idea ever existed in the first place? Sure, the development would be much more painful, and budget for implementing 2xCBE compared to RSX would be much higher?
Sorry, I wasn't following exactly from the start of the generation.
The idea never really got much traction besides probably some very early meetings... the dual CELL set-up would have never matched the rendering speed required (for all the flak RSX gets, it is better to have it than to simply have a second CELL device acting as GPU as CELL has no dedicated graphics hardware whatsoever while even the newer LRB chip from Intel has dedicated texture units which are very hard to efficiently substitute with software solutions).
Cheezdoodles
07-Sep-2009, 16:54
While the Cell is a reasonably fast CPU, it completely and utterly sucks for doing GPU work compared to a GPU. Dedicated hardware is there for a reason.
Its just not an efficient solution. Even if we put in several cells, any modern GPU will completely rip it to shreds at doing gpu work.
I Have a question. Why exactly was the original 2xCell design abandoned, if such an idea ever existed in the first place? Sure, the development would be much more painful, and budget for implementing 2xCBE compared to RSX would be much higher?
Sorry, I wasn't following exactly from the start of the generation.
Because 2x Cell would give crappy graphics compared to a X360 with a Xenos. It would also require tremendous amount of work, and seeing as the results would be crap anyway, way better solution to just put a proper GPU in, save the devs the time and increase the graphics potential
Shifty Geezer
07-Sep-2009, 17:12
While the Cell is a reasonably fast CPU, it completely and utterly sucks for doing GPU work compared to a GPU.Just for accuracy, Cell completely and utterly sucks at some GPU work. Some stuff Cell is on a par with, and some other stuff (certainly when PS3 was being designed) Cell is better than a GPU, only there's not much room for complex vertex shaders when you can't texture them! Although we've discussed before theoretical software renderers which could get past some of the texturing limits for a particular engine. Not that dual Cell would ever be a replacement for the current design.
MrCarrefour
11-Sep-2009, 22:29
Ok, I understood some of the GPU work can be offloaded to the cell processor.
This is a good option for the developer.
Anyway .. the SPE are vectorial processors, so .. they must be good for this, if not, why the spe are a vectorial processor?
This can be the reason the Ps3 has a lower GPU than xbox360, isn't it?
It should be nice to know how much of the normal GPU work is offloaded to the cell processor in the most famous games .. does anyone know?
Shifty Geezer
12-Sep-2009, 09:35
"Vector" doesn't mean vector graphics, but a type of data packaged up. Any processing that can be mapped to several numbers and sums at the same time fits to vector processing. Obviously 3D space is one such task, with X, Y and Z data components to describe each point, and that's why Cell is good at vector work. Texture work OTOH is all about memory access, which throws up a lot of problems about latency and waiting for textures to be fetched so you can shade the triangle.
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