Anti-aliasing and unified memory architecture

FiringSquad: You said earlier that EDRAM gives you AA for free. Is that 2xAA or 4x?

ATI: Both, and I would encourage all developers to use 4x FSAA. Well I should say there’s a slight penalty, but it’s not what you’d normally associate with 4x multisample AA. We’re at 95-99% efficiency, so it doesn’t degrade it much is what I should say, so I would encourage developers to use it. You’d be crazy not to do it.

You know even though we’re in a high def resolution world with Xbox 360, well you know at standard definition with today’s TVs jaggies look bad, really bad with standard definition. In hi-def everything is so sharp, that when there are aliasing issues, you’re really going to see the jaggies there so I think anti-aliasing is just key and we have a great anti-aliasing story.

And of course you do know that while we support hi-def we will still output to standard def, although Microsoft has said that hi-def is the target platform, don’t think “oh well, it won’t work on my standard definition television”.

FiringSquad: How many textures per pixel are you performing per pass?

ATI: 4 textures. We have 4 texture units. And we don’t have separate texture instructions, the shader just goes and it get textures and it applies them.

FiringSquad: Microsoft has announced 1080i support, but are there any plans to add support for 1080p?

ATI: I think 720p and 1080i are the sweet spot that developers are going for and that’s what we’re going to see in the next few years, for the next five years really as the main resolutions. It will be awhile before 1080p becomes standard. I think 720p would be the best to go for, and 1080i is supported as well of course. So hopefully developers will be doing, or at least the best would be 720p, 4xAA. You’d get a teriffic image there.

FiringSquad: With the unified memory architecture, do you feel the VPU and CPU will be fighting over the available bandwidth?

ATI: We’ve optimized everything enough where I don’t think it’s going to be a problem. You know, we’ve had silicon since November so I can tell you it’s not going to be a problem. We were worried, you know obviously when you integrate the unified shaders and the EDRAM, we were a bit worried that there could be efficiency problems in the unified shaders, that there could just be general problems with EDRAM. And of course we’re still looking, but so far it has all worked out, it isn’t a problem. So we’ve had this debate for awhile. Not that we didn’t have bugs. [laughs] None of them were our fault.