Cell and RSX : their relationship.

Was there ever a doubt? Even EE does it, Xenon does it too, and probably BroadWay will do it too.

 

More importantly, you guys are forgetting that HDR, when not done by ping-ponging between render targets, is achieved using floating point blending in the frame buffer.

This is a specialised piece of fixed-function hardware in the ROPs. NVidia claims (quite reasonably) a peak of 106 GFLOPs in 6800 Ultra (16-bit FLOPs, not 32-bit). It'll be slightly more in RSX.

That's around half the capacity of the 7 SPEs used up...

Then there's the FP16 texturing. That's another 154 GFLOPs of fixed function hardware in 6800 Ultra (approximately 50% more in RSX) that you'd need to execute on Cell.

Whoops, you've completely utilised Cell's SPEs solely in HDR texturing and blending.

Jawed

 

I think what they meant by cell helping with hdr is that an spe could be used to scan the output of the previous frame and provide tone mapping parameters for the next. this is of course not needed if rsx is not the bottleneck, but reading back/writing out huge buffers is no small task and if it can be overlapped, then it's a win.

(i didnt look up actual flop/bandwidth numbers, so it's theoritical)

 

It's not the transistor count that matters for cost, but die size and yield. Generally a chip with more transistors will be bigger, but if the numbers are close the chip with fewer transistors could actually be bigger. Of course by saying should you were probably just condensing what I'm saying to a single word. Definitely better word density on your part.

 

LOL, yeah that's what I was going for. 8)

It's certainly the case that more transistors doesn't always mean more die size. But RSX has so many more transistors that I would just be shocked otherwise. 234 million for Cell vs more than 300 million for RSX. Also, they'll be produced on the same process in Nagasaki, and should both include some sort of 'redundancy' to increase yields. One SPE able to take a bullet on Cell, and on RSX whatever the alluded to redundancy is - probably some pixel pipes I would imagine.

 

*Ouch*

 

whoa

 

They can when doing the thing they were specifically designed to do, in other words ROPs, like framebuffer blending (used in HDR), stencils/z resolve, AA, etc.

Specialized hardware will tend to outperform more generalized hardware, at the specific tasks it was optimized for.

In a good design, you will put generalized hardware where you need generalized hardware, and you put specialized hardware where its best to put specialized hardware.

Use the right tool for the right job. You don't use a screwdriver to pound in a nail, even though in a pinch you might get it to work.

 

Jawed: How did the Getaway demo manage HDR using mostly Cell if SPEs are gonna be choking on it? PEACE.

 

Didn't the demos at e3 all have 6800ultra sli cards in them ?

 

I'm referring specifically to the Getaway demo, which is claimed to have run mostly off Cell. Didn't Phil Harrison in the presser specifically refer to the Cell in relation to the HDR effects? I know there was a thread on this, and it was debated before. Was it concluded that HDR was running off the GPU? Besides which, we heard that the hw was anywhere from SLI 6800Us to a G70 to G70s in SLI. PEACE.

 

I'm not sure thus the ?

Anyway it doesn't matter if its a 6800ultra sl or a g70 or a g70 sli . All that is is power . The 6800ultra would have been more than enough to do those scenes with hdr

 

He's referring to the Masa Chatani claim that The Getaway demo was done on Cell only.

 

But they must have used a rasterizer in the video card to display the images. I think the confusion is using only a rasterizer in the video chip was not done since the psx.

 

Prolly because someone, somewhere, is being economical with the truth.

Jawed

 

Must they?

A CPU could do rasterisation, it just relatively would not be nearly as fast as dedicated hardware.

Anyway, while The Getaway may have been doing this (everything, rasterisation included) purely for technical demonstration purposes - and I've seen it emphasised a couple of times now that it was just a tech demo - games obviously won't. Doesn't mean you wouldn't do other stuff on Cell graphically if you wanted, though, or a subset of what The Getaway was doing, before passing to RSX. Where you'd split work between them though, I don't know.

 

Simple answer: Cell only demos were using 2 Cells.

 

No. They were using one Cell and the 6800 GPU with SLI. :?

 

I think I read somewhere the Terrain demo was 2x2.4Ghz CELL chips and the getaway was 'mostly done on one CELL', whatever mostly means.