XBox 360 GPU Explained

[bapenguin]

HardOCP (http://www.hardocp.com/article.html?art=Nzcx) sat down with ATI to get the lowdown on just what the XBox 360's graphic unit is capable of. It's a pretty amazing piece of tech designed from the ground up for the XBox 360 Console.Inside the Smart 3D Memory is what is referred to as a 3D Logic Unit. This is literally 192 Floating Point Unit processors inside our 10MB of RAM. This logic unit will be able to exchange data with the 10MB of RAM at an incredible rate of 2 Terabits per second. So while we do not have a lot of RAM, we have a memory unit that is extremely capable in terms of handling mass amounts of data extremely quickly. The most incredible feature that this Smart 3D Memory will deliver is “antialiasing for free” done inside the Smart 3D RAM at High Definition levels of resolution. (For more of just what HiDef specs are, you can read here. Yes, the 10MB of Smart 3D Memory can do 4X Multisampling Antialiasing at or above 1280x720 resolution without impacting the GPU. So all of your games on Xbox 360 are not only going to be in High Definition, but all will have 4XAA applied as well.

Sweet...very very sweet.

[TrackZero]

Nice. I love how much new stuff microsoft did with the 360, instead of just cranking up the usual clock speeds, there's lots of core design changes on their bus and memory to improve utilization.

[sTubbs]

Good article. It is nice to see something written in a level of English that I can understand - tech jargon just gives me a headache. Anyways, I have to wonder about this cooling system being adequate, as Hard OCP is not the only place that has expressed worries. MS keeps reassuring people that it will be, however, so I guess we shall see.

[Morratut]

I like the way MS seem to be giving decent amount of details on actual specs,abilities and online features. Whilst also trying to protect their most sensitive parts of the console. :)

[Metal Jesus]

Is it just me or does the XBOX 360 seem more tangible than the outrageous claims of the PS3. Dont' get me wrong, I'm no fanboy of either really... it just that right now I have a hard time believing that the PS3 is going to be that much better than the 360.

[voodoo401]

Well I hope that they would release info since they will be shipping it in6 months or less as for Sony they are not going to ship it this year so why release spec.?

[ColdForged]

Is it just me or does the XBOX 360 seem more tangible than the outrageous claims of the PS3.
One company is explaining and showing a lot. The other is doing a lot of hand-waving and video showing. I don't think it's just you. That's not to say that the PS3 won't have power. But taken merely in terms of the detail being provided by Microsoft of all aspects of the console -- from technical specs to the next-gen Xbox Live features -- I definitely "feel" more confident about what they'll be providing come ship date.

[falak]

It seems the 360 is going to have a lot of features to help programmers, even at the hardware level. And if we learnt anything from the last generation, it's that the power of a console doesn't really matter (to a point). I think Microsoft has made some very intelligent moves.

[Mason]

I wish we could get some discussions of this sort from Sony, beyond Cell diagrams and marketing phrases. These are the details that will really differentiate the consoles.

Of course you can't give much credit to MS, since [H] had to talk to ATI guys to get anything above the MTV intelligence level.

[crashedout]

I think that is the deal, ATI and Nvidia talk about the gpu's on their own. There have been rumors of both of them showing presentations this week about their respective GPU's. I will not trust Sony launch hype anymore since the PS2, I will however wait and see and pick up their box on its first price decrease/hardware revision. The 360 is in my house on day one.

I agree with the ATI, jaggies===bad. Smooth move building a specialized high speed core to elimnate them with minimal performance hit and kudos to MS for requiring the devs to use it. When you get an HDTV you will thank them.

[Reanimated]

I wonder how much of a performance hit the PS3 GPU will take to do 4XAA since it doesn't have this kind of architecture.

I know that enabling ANY level of AA on my 6800 Ultra has a VERY SIGNIFICANT impact. I usually just leave AA turned off because of the performace dip it causes.

This notion of "AA for free" is intriguiging to me. My next PC card may be from ATI if they are incorporating this into their PC cards.

[sTubbs]

I wonder how much of a performance hit the PS3 GPU will take to do 4XAA since it doesn't have this kind of architecture.

I know that enabling ANY level of AA on my 6800 Ultra has a VERY SIGNIFICANT impact. I usually just leave AA turned off because of the performace dip it causes.

This notion of "AA for free" is intriguiging to me. My next PC card may be from ATI if they are incorporating this into their PC cards.

Unfortunately, the article said not to expect this anytime soon in the PC world. It is definitely the most intriguing aspect of the GPU. The fact that it can handle so many traditionally processor intensive tasks means that the the RAM and CPU can be used for things like physics. Good stuff.

[Adam Blue]

I'm glad AA is taken seriouisly. In Hi-def, jaggies looked bad. the term "AA for free" is effin awesome.

[Reanimated]

Unfortunately, the article said not to expect this anytime soon in the PC world. It is definitely the most intriguing aspect of the GPU. The fact that it can handle so many traditionally processor intensive tasks means that the the RAM and CPU can be used for things like physics. Good stuff.



Yeah, I just finished reading. That kinda sucks... seems like a no-brainer. Maybe we'll see it down the road. My 6800U should last me a good while anyway.

[kokyunage]

What kind of antialiasing, if any, do you get at the higher HD resolutions?

[sTubbs]

What kind of antialiasing, if any, do you get at the higher HD resolutions?

The 360, thanks to this embedded ram in the GPU, will have 4xAA on all games at all resolutions.

[Nath5000]

We all have to keep in mind that not only are the games shown at E3 designed on alpha kits with less CPU power, but they also only have ATIs top of the line current gen PC GPUs. This means that the beta kit with this completely different graphic architecture could give the post launch xbox 360 games designed for that GPU a completely different graphic capability. By the time they get the beta kits out with the real stuff, the games will have already been designed for the lower spec, and if anything they will just be tuned to work amazing on the heavy hitting hardware. My guess is that the difference between launch and 2 year into the generation xbox360 games will be far greater than the difference between halo and halo2 because those games will be designed completely from the ground up for this new graphics architecture in mind.

that being said, a possible "halo 3" using the unique GPU architechtural advantage and being released along side ps3 could be a lot harder of a hit for sony than we can imagine, ESPECIALLY if ps3 doesnt have a killer app by that time aside from sports games.

[Talanvor]

I'm a little curious as to why this won't happen on the PC. If they can stick it in the 360 they can stick it in a PC. And I agree, if ATi can pull off AA without making a huge impact, their's will be the next one I buy.

[Ernst_Jager]

Probably because Microsoft paid them lots of money to make this.

[StGeorge]

One thing to keep in mind is that before the Xbox launchthe dev-kits were actually more "powerful" (specs-wise, I believe they were 1.5 ghz boxes with a slightly less powerful Nvidia card) than the final Xbox production machine. The final Xbox still managed to outperform the dev-kit. Now that the dev-kits are about 1/3rd the power of the final, just imagine what's in store...

[bapenguin]

I think the reason you don't see this kind of article from Sony is, they simply aren't that far along in their dev cycle.

[chechenepiphany]

Yeah, i have to say, ms is being a lot more open about architecture. all ive heard about the ps3 so far is that "ITS GONNA HAVE LIKE 10 CORES11111111111". which is a little hazy, especially considering that AMD and Intel are currently struggling with putting 2 and 4 cores efficiently on one processor. i realize that this is different with consoles, but as of yet ive heard no reasonable explanation of the ps3s actual artchitecture. dont take me wrong, i own playstations one and two, i just havent seen anything serious or particularly reasonable. of course, the ps3 is 6 months further down the road.

[Phades]

Probably because Microsoft paid them lots of money to make this.

That's actually probably somewhat right. Microsoft paid them to develop this and owns the rights to the chip. They didn't do what they did last time with Nvidia, this time they actually own the chip designs so they can be in a better position when it comes time to cut costs.

[bobbler]

The cell is by far the most public of any of the chips going into the console, you can get the complete info about it from IBM. As far as I'm concerned the Xbox360 CPU is the biggest mystery of the consoles, they don't give the nitty gritty specs of it. (not including the entire N-Rev).

I explained what the cell is in another thread (probably on page 2-3 now), its not all that outrageous -- its just far more customized for its job than the other stuff floating around. Its more akin to previous generation console CPUs that were custom made for the consoles. Whats so hard to understand? The bus system of the PS3 also has a ton of info out about it thanks to rambus bragging about technology (look up flex I/O).

The only info that isn't getting out about the ps3 is the GPU, which is mostly because of NDAs. Its based off the G70 core which anyone who has info about it has some hefty NDAs hanging over their head.

I can give you an educated guess about the PS3 GPU though. 24 Pixel shaders, 10 Vertex shaders, 4 shader ops per cycle per shader unit -- 136b shaders/cycle. Pretty comparable to ATI's 96b shaders/cycle, they have the advantage of being fully customizable shaders (48 generic shaders, but only 2 shader ops/cycle). So depending on the use ATIs is more versatile, but nVidia's has more power. Different games will stress the strengths in different ways, but they should be pretty similar overall. The only difference really is if for some reason you wanted more than 10vertex shaders (20 on ATIs), you'd be out of luck -- for pixel shaders they are in the same boot, kind of. ATI can spend all 48 of its shaders on doing pixel shaders, meanwhile nVidias can spend its 24, but it will still have its 10 vertex shaders to spend on top of it. Both designs have their drawbacks, of varying degrees.

[Kelegacy]

The cell is by far the most public of any of the chips going into the console, you can get the complete info about it from IBM. As far as I'm concerned the Xbox360 CPU is the biggest mystery of the consoles, they don't give the nitty gritty specs of it. (not including the entire N-Rev).

I explained what the cell is in another thread (probably on page 2-3 now), its not all that outrageous -- its just far more customized for its job than the other stuff floating around. Its more akin to previous generation console CPUs that were custom made for the consoles. Whats so hard to understand? The bus system of the PS3 also has a ton of info out about it thanks to rambus bragging about technology (look up flex I/O).

The only info that isn't getting out about the ps3 is the GPU, which is mostly because of NDAs. Its based off the G70 core which anyone who has info about it has some hefty NDAs hanging over their head.

I can give you an educated guess about the PS3 GPU though. 24 Pixel shaders, 10 Vertex shaders, 4 shader ops per cycle per shader unit -- 136b shaders/cycle. Pretty comparable to ATI's 96b shaders/cycle, they have the advantage of being fully customizable shaders (48 generic shaders, but only 2 shader ops/cycle). So depending on the use ATIs is more versatile, but nVidia's has more power. Different games will stress the strengths in different ways, but they should be pretty similar overall. The only difference really is if for some reason you wanted more than 10vertex shaders (20 on ATIs), you'd be out of luck -- for pixel shaders they are in the same boot, kind of. ATI can spend all 48 of its shaders on doing pixel shaders, meanwhile nVidias can spend its 24, but it will still have its 10 vertex shaders to spend on top of it. Both designs have their drawbacks, of varying degrees.

I've come to the conclusion that you're a pretty smart guy. So, what are you doing on Evil Avatar?? You are intelligent, seem to be a devil's advocate when talking about gaming, and your posts are informative and enlightening.

So, I ask again, what the fuck are you doing here!!? :)

(just kidding, i know a few intelligent people that, when I see their names in a thread, i know that i'll enjoy their words or company. I dont have to worry about intangible remarks revolving around stroking off one particular company or nut-biting the other. I just wanted you to know that you've officially joined those sparse ranks. Welcome.)

[bobbler]

Heh, thanks =o

I try to suppress my preference of certain products (although they slip out at times, tee hee) when posting, because they don't do anyone any good...

[mister_slim]

Nice. I love how much new stuff microsoft did with the 360, instead of just cranking up the usual clock speeds, there's lots of core design changes on their bus and memory to improve utilization.
It's nice the hardware guys realized they're designing a console and not a PC. Now we just need to get through to the software people.

[Carnifex]

Since ATI's GPU approach is (possibly) more flexible, couldn't it enable greater diversity in types of games for the 360? nVidia will have an upper bound for i.e. amount of vertex operations per cycle, which in turn limits what can be done in a game and hence the types of games for the platform, but with the ATI GPU one can for example trade off graphical effects with more destructible environments.

Edit: Forgot to proclaim my love for 4xAA at HD resolutions :D

[bobbler]

Since ATI's GPU approach is (possibly) more flexible, couldn't it enable greater diversity in types of games for the 360? nVidia will have an upper bound for i.e. amount of vertex operations per cycle, which in turn limits what can be done in a game and hence the types of games for the platform, but with the ATI GPU one can for example trade off graphical effects with more destructible environments.

Edit: Forgot to proclaim my love for 4xAA at HD resolutions


Graphically maybe, but you gotta understand... The advantage of being able to use a ton more vertex shaders is easily thrown away by the fact that you won't get as many pixel shaders. Its a balance situation, thats where the flexibility comes from -- you won't see huge differences if any, I'm betting you won't notice much of a difference if any between the graphics (if anything I think the RSX will be able to pump out a little more shiny stuff, but it will be negligable). A game with pure vertex shader effects might not be the most impressive graphically (or maybe it would?), but you could probably pull off some interesting things -- this I agree.

The differences come in the fact that you can have like 21 vertex shaders and 27 pixel shaders -- you won't be able to do that on the RSX, you get 10 vertex (20 ATI equivalent) and 24 (48 equivalent) pixel shaders no matter what. There won't be any 'wasted' on the ATI's chip, its efficient.

I agree with the 4xAA being a nice addition -- at 1920x1080 AA doesn't arguably do all that much (I know from PC, I never bother with AA at 1600x1200, 1080 is a few more pixels than that -- but since its nearly free, no reason not to use it no matter the res), but at 720p it will surely be appreciated (I haven't seen an HD tv for more than a few minutes, and definately no games on it, so I haven't really experienced the effect it has beforehand).

[Carnifex]

A game with pure vertex shader effects might not be the most impressive graphically (or maybe it would?), but you could probably pull off some interesting things -- this I agree.
Yes, I was thinking in terms of gameplay, not graphics. Personally I don't think the Xbox has enough diversity in games, which might be because of hardware limitations but I'm sure the reasons are many. The big push now is graphics, but it would be nice to have something that can help enhance gameplay as well, so we don't just end up with more shiny versions of the previous generation games. Of course having three CPU cores should also provide ample opportunity to create interesting things.

[mister_slim]

Yes, I was thinking in terms of gameplay, not graphics. Personally I don't think the Xbox has enough diversity in games, which might be because of hardware limitations but I'm sure the reasons are many. The big push now is graphics, but it would be nice to have something that can help enhance gameplay as well, so we don't just end up with more shiny versions of the previous generation games. Of course having three CPU cores should also provide ample opportunity to create interesting things.
I would guess the diversity problem on the Xbox is for the same reason as the GC: The types of games people owning the system buy are the genres that thrive.