R500 + eDRAM... what are the benefits?

[Acert93]

Specifically, what features/savings is this eDRAM going to REALLY give. We hear it has 256GB/s of effective bandwidth, but it is also 10MB. How are developers planning to use this? Will it help out

HDR?
Motion Blur?
AA?

What other features will it help? Where will it not help? Can the Framebuffer be titled? Can you move the framebuffer output to the main memory to do more advanced features and then output that? I think someone noted that the Xbox 360 article at Anand noted 1080p is supported--how?

Obviously spending about 90M transisters on the eDRAM must have some huge benefits. So what do you guys expect to see out of it and how will it be used?

On a related note, it looks like the RSX has FP32 blending (128bit?) and the R500 has FP10 (32bit?) if I caught the blurbs correctly.

1. Can we realistically expect FP32 to be used performance wise? Why/Why not?
2. According to the Nvidia demo at the Sony conference there is a pretty big difference, is that about what we should expect in HDR difference between the two?
3. How will the higher percision HDR affect bandwidth?

 

[jvd]

It seems like in that 10mbs you can fit a 2x fsaa 720p framebuffer pretty nicely .

Perhaps even 4x fsaa .

To me thats pretty good and will give them fsaa for free from my understanding


HDR well i don't know too much about this i know on the nv40 hdr doesn't work with fsaa . Perhaps on the rsx and the r500 they have it working together ?

motion blur ? They should be able to add that using shaders

I'm sure there are others that can comment more and perhaps correct my comments


edit


as for the percision i would think a 128bit hdr would take up way to much bandwidth to make it widely used . I think this was something as a marketing bullpoint for the rsx desktop versiion . I thik you will see fp16 in the games

 

[Riddlewire]

Todd Holmdahl explicitly states that X360 will not support 1080p (but WILL support VGA) in this interview - http://www.extremetech.com/article2/0,1558,1817025,00.asp

 

[DemoCoder]

The big question is, if they support HDR, and if so, does HDR work with compression. If not, say bye bye to those "effective" 256gb/s figures

 

[jvd]

Todd Holmdahl explicitly states that X360 will not support 1080p (but WILL support VGA) in this interview - http://www.extremetech.com/article2/0,1558,1817025,00.asp

It should have no trouble supporting that res . If it can do 1080i i don't see why it can't do 1080p

ET: All Xbox 360 games have to support 720p at a minimum but will have standard definition modes as well, some games are supporting 1080i. What about 1080p? Some new displays can handle 1080p…

TH: We have developed a box that supports all the devices that are out on the market right now. And we'll continue to look if there are other things that are being developed, we'll continue to consider those things.

ET: So, to be clear, yes it can to 1080p, or no it can not?

TH: It does not support 1080p. It supports all of the TV sets that are out on the market right now. All the sets that people are using to play games right now.

 

[Shifty Geezer]

'Coz 1080p needs twice the throughput, assuming its 60 fps and not 30fps.

 

[Glonk]

The tv-encoder is the limitation.

 

[Pozer]

'Coz 1080p needs twice the throughput, assuming its 60 fps and not 30fps.

From my understanding the video signal only has to be 1920x1080 at 60Hz to declare 1080p support. This has more to do with tv-out chip of the ps3 than its power. A good analogy would be to that my PC monitor supports 1600x1200 at 85Hz but Doom3 only runs at 21 fps not 85fps. 1080p has nothing to do with fps.

 

[Shifty Geezer]

XB360 supports 1080i at 60fps. 1080p at 60fps requires twice the resolution so needs twice as much graphical oomph-bandwidth-malarkins (to use a technical term). XB360 could potentially output at 1080p at 30fps regardless of refresh rate if the output technology is included to supply a compatible signal. For true 1080p, 60fps, the hardware presumably isn't up to it (bandwidth limited or something?). As to how well PS3 supports it, we'll have to wait and see. It might support the output, but might be at lower frame rate.

 

[pegisys]

it wouldn't need twice the resolution I'm sure when it's running at 1080i it's progressive scan internally I'm sure it's the tv out connector not to the 1080p spec, and if they plan on supporting monitors that can do 1920X1080 it will be progressive scan as well

 

[Inane_Dork]

A 32 bit color and 32 bit Z/stencil buffer do not fit in 10 MB. There seems to be some confusion on that topic.

The eDRAM will alleviate a lot of the render target bandwidth, color, Z, and stencil. So cube reflections, shadow maps, stencil shadows, post processing effects, etc. should all take less RAM bandwidth. Of course, just rendeing models and particle effects will take less RAM bandwidth too, but it's more than just the final screen. It helps with anything you render to (I would guess).

 

[Acert93]

From the RSX thread Jaws touched on the AA and how the eDRAM benefits.

So how does it benefit HDR? Is the framebuffer bandwidth something that can overcome the HDR bandwidth issues or is that a limitation that the eDRAM framebuffer cannot help with?

 

[Wunderchu]

from the second last page of that interview with Todd Holmdahl that Riddlewire posted a link to:

You take a look at the embedded DRAM, for example. We put over a million gates in the embedded DRAM that do processing internal to the embedded DRAM. To do things that would normally be done on the GPU side. It helps with some of the stuff that happens during the rendering process, which means you don't have to shift that stuff back and forth across the memory bus.

 

[blakjedi]

Simple question so R500 doesnt do do HDR or doesnt do it well? The use of HDR in "the getaway" demo on PS3 stunned me. That is the lighting I have been waiting for for five generations...

 

[Dave Baumann]

I've had a little discovery on "C1" (which, evidently, is the real codename for R500) - this was just a quick chat, so detials are sketchy.

Float Blending/Filtering is supported and this, IIRC, is orthogonal with FSAA. I think its a bit of a misnomer purely consider what can "fit into" the eDRAM since this is not where the fully rendered pixel reside.

Evidently the system is automatically set up to do a Z only pass first; now although geometry isn't binned, evidently they are saving the max extents so they can use that somehow in the shader pass - not quite sure how that works yet. The Z/Stencil is double pumped from the normal pixel rate so the Z pass is twice as fast as just pure pixel filling.

With luck, I should have a chat with the senior architct in about 2 hours, however he's somewhat busy as he's preparing for a press confernce tomorrow - hopefully I'll be able to chat with him sometime whilse I'm here, so if you have questions...

 

[blakjedi]

I've had a little discovery on "C1" (which, evidently, is the real codename for R500) - this was just a quick chat, so detials are sketchy.

Float Blending/Filtering is supported and this, IIRC, is orthogonal with FSAA. I think its a bit of a misnomer purely consider what can "fit into" the eDRAM since this is not where the fully rendered pixel reside.

Evidently the system is automatically set up to do a Z only pass first; now although geometry isn't binned, evidently they are saving the max extents so they can use that somehow in the shader pass - not quite sure how that works yet. The Z/Stencil is double pumped from the normal pixel rate so the Z pass is twice as fast as just pure pixel filling.

With luck, I should have a chat with the senior architct in about 2 hours, however he's somewhat busy as he's preparing for a press confernce tomorrow - hopefully I'll be able to chat with him sometime whilse I'm here, so if you have questions...

Wavey.. can you explain in English whenever you get a chance for us non programmer types ? I want to be as excited as you seem to be... plus if you could answer my question above your post I'd appreciate it.

Thanks muchly sir!

 

[PC-Engine]

Simple question so R500 doesnt do do HDR or doesnt do it well? The use of HDR in "the getaway" demo on PS3 stunned me. That is the lighting I have been waiting for for five generations...

Not really sure The Getaway demo is using HDR. It seems it was using Spherical Harmonics or something.

 

[DemoCoder]

Questions:

a) can AA be enabled on HDR FP render targets
b) does it still compresss HDR framebuffers
c) any compressed DXTC-like formats available for HDR?
d) let's here more about the tesselation/geometry shading
e) when doing HDR+AA, since it does not fit into eDRAM, how is this accomplished beside developers doing tiled passes manually? Does the eDRAM support hardware spillage of its contents and during blending, does it fetch any contents that have been spilled to main ram?
f) 48 ALUs, 16 "pipes", 8 ROPs, is that right?
g) dynamic branching performance?
h) gradient instructions?
i) can it double pump-Z in 2xFSAA mode (32-zixels per clock?)
j) any special HW support for tone-mapping algorithms

oh, and does it have a TMDS transmitter to support real DVI/HDMI out?

 

[Acert93]

Thanks Dave. You are just toooo cool man

 

[Dave Baumann]

a) can AA be enabled on HDR FP render targets

Yes, this is orthogonal, IIRC.

f) 48 ALUs, 16 "pipes", 8 ROPs, is that right?

Actually, it appears to be 48 threads being processed from 64 active, so all the ALU's sound like they are independant.