Xbox 360: First Look at Final Hardware

[Lysander]

It's looking that way. It's certainly a logic issue as there's bandwith out the wazzoo in the e-Dram. Could be devs just don't know how to work the e-Dram well enough yet.

Pics of kameo don`t appear to have jags (except on kameo herself). The original poster is not precise.
Uh, I would like to hear Dave on this.

 

[mckmas8808]

The latest interview of Major Nelson on the Chris Pirillo(sp?) Show clarified this, the only way to store on the drive itself is to rip from a cd, or whatever you download from the marketplace.
I think msn music at some point or another will be tied into the 360, but thats my speculation.

So basically you can rip music from a CD-RW to the 20 Gig HDD? And then use that to play in games?

 

[hey69]

. Kameo is a launch game where devs had little time and dev kits came slow


huh? isnt this in development for ages ?

 

[Titanio]

Images from the recent nFactor2 demo were labelled as direct-captured from a devkit, but they are 1024x576, with 2xAA. Also, in NBA2K6 images in gamespot, 1024x576 images have no noticeable jaggies while other 720x1280 / 1280x720 images at IGN have jaggies all over, so internal resolution may be tweaked for these games to fit in eDRAM for higher frame rate.

EDIT: NFL -> NBA

You think they're rendering internally at 1024x576 with 2xAA and then scaling up to 720p?

edit - it is just a little coincidental that a 32bit framebuffer and colorbuffer fit comfortably in the eDram at that resolution and with 2xAA (takes 9MB, I think?).

 

[scificube]

Sorry it's not Madden but NBA It seems they use DOF for audience.

I stand corrected. It still seems wierd DoF alone would knock AA out of the picture.

. Kameo is a launch game where devs had little time and dev kits came slow


huh? isnt this in development for ages ?

Yes that's true, but not on the X360. Rare had to deal with the same alpha and beta kits etc and learning issues that everyone else did and still have to.

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Couldn't it appear those pics had AA on if they were shrunk from pics at 720p with no AA?

 

[pegisys]

huh? isnt this in development for ages ?

yeah but it has switched architecture how many times now. from gamecube to xbox to the g5 macs microsoft were calling dev kits and to the final hardware of the 360 only a few months ago

that's probably the problem with most games, maybe they tuned there game to the older dev kits and the transition is not that easy. it was a big just in speed and architecture

 

[hadareud]

a few things seem weird in this article. Also, the author of the original at heise does not seem to exactly have a bias towards xbox to say at the least

 

[Squeak]

Does this mean that AA does have a noticable hit on performance after all, or only with some effects?

 

[Titanio]

Does this mean that AA does have a noticable hit on performance after all, or only with some effects?

It would be nice to have some info on this, it's a little puzzling (PGR3 is at 2xAA also, apparently).

Reading Dave's Xenos article, I can't seem to find the claimed performance hit with 2xAA. 4xAA is claimed to have 95% of the performance of 2xAA.

I suppose the more other things you're doing, that more potential there is for that to change. Why though, I've little idea, bandwidth shouldn't be a problem. I'm also a little confused as to why they'd avoid tiling - the main memory bandwidth requirement for that would seem to be minimal, unless I'm misunderstanding something.

Also, would MS allow devs to render internally at a lower resolution and then scale up to 720p?

 

[pjbliverpool]

I'm also a little confused as to why they'd avoid tiling - the main memory bandwidth requirement for that would seem to be minimal, unless I'm misunderstanding something.

Doesn't tiling double up on the rendering of polygons which straddle the different tiles?

 

[ERP]

Doesn't tiling double up on the rendering of polygons which straddle the different tiles?

There is some duplicate work, mostly on the vertex side. You also have to build a display list with the entire scene in it if you want to use the predicates. Depending on how you organised/submitted the data this could be large.

For any practical setup I can think of, the GPU will be idle during the GPU->Mem copy. Theoretically you might be able to double buffer in the EDRAM and render during the copy, but at the cost of increasing the tile count and therefore additional duplicate work.

It's going to take a few rounds of software to find out where the sweet spot is with tiling, resolution and AA.

 

[Titanio]

There is some duplicate work, mostly on the vertex side. You also have to build a display list with the entire scene in it if you want to use the predicates. Depending on how you organised/submitted the data this could be large.

For any practical setup I can think of, the GPU will be idle during the GPU->Mem copy. Theoretically you might be able to double buffer in the EDRAM and render during the copy, but at the cost of increasing the tile count and therefore additional duplicate work.

It's going to take a few rounds of software to find out where the sweet spot is with tiling, resolution and AA.

This makes sense.

To clarify, the idle time with the eDram->mem copy for tiling is the worst offender in terms of cost? Or just another expense?

Do you know or can you say if native resolution can be lower than 720p?

Sorry for the questions. I was always assuming that eDram stuff was something that could be very simply "switched on" once it was there, with little effort.

 

[ERP]

You can work out exactly the time it takes for the tile copy with the info in Dave's article. It runs at peak bandwidth.

It's a combination of things and the costs are going to be very scene dependant. Even if you can run at 95% efficiency with say 2 tiles, that's still 5% you're loosing. It not really much of an issue if you plan for it at the start, but you have to bear in mind that the majority of launch titles are based on guesses and often incorrect assumptions, they are commonly optimised late when it's impractical to redesign renderers, and 5% can be the difference between 60fps and 30 if it comes down to the wire.

None of the early hardware supported tiling and I'd bet money that any dev targeting launch who can't time and test a feature is going to err on the side of caution.

 

[Titanio]

Cheers ERP, makes sense.

On this point:

"You also have to build a display list with the entire scene in it if you want to use the predicates."

Is this just the list telling you what belongs to which tile?

edit - apparently AA is mandatory, i.e. 2xAA at least, not sure then what the article is saying. If some devs were reducing resolution then, to avoid tiling (which would be necessary at 720p with 2xAA), it would seem to be a rather silly situation, as the image would then just be scaled up again, for 720p displays at least, enhancing any small aliasing left over after 2xAA. The question remains though, if devs can use native resolutions lower than 720p..

 

[expletive]

Cheers ERP, makes sense.

On this point:

"You also have to build a display list with the entire scene in it if you want to use the predicates."

Is this just the list telling you what belongs to which tile?

edit - apparently AA is mandatory, i.e. 2xAA at least, not sure then what the article is saying. If some devs were reducing resolution then, to avoid tiling (which would be necessary at 720p with 2xAA), it would seem to be a rather silly situation, as the image would then just be scaled up again, for 720p displays at least, enhancing any small aliasing left over after 2xAA. The question remains though, if devs can use native resolutions lower than 720p..

MS stated all developers need to to make games that run at 720p and have 2xaa. If they were going to scale everything to 720p regardless, then developers really have nothing to do with it since its the scaling chip doing all the work, so theres no reason to "require" it. This would be a real play on words and bad form from MS if it were true though.

Incidentally, doesnt the Xenos article explain how the EDRAM manages 720p and applies the effects with no penalty in the 10MB space? Surely developers must have also known this information so why all the discussion about a lower native res?

On another note, 1080i clearly listed:
http://www.xbox.com/en-US/xbox360/factsheet.htm

So maybe the translation/reporting is a little off...

J

 

[chosen_colette]

This is wierd. I thought Dave's article showed how the e-Dram could handle 720p+AA. I can imagine this tweaking may be necessary with the nFactor2 demo if they're trying to do AA+(HDR/DoF/etc.) I don't see where Madden is using effects that would preclude AA from being used...unless they're using DoF and it's more costly that I thought.

funny, how everyone seems to think DoF is bandwidth intensive for the 360, it may very well be, but keep this in mind, gamecube does DoF 100% computationally for free because of the way it handles textures in cache . perhaps microsoft yet again fails to understand efficiency over raw power

 

[Titanio]

Incidentally, doesnt the Xenos article explain how the EDRAM manages 720p and applies the effects with no penalty in the 10MB space? Surely developers must have also known this information so why all the discussion about a lower native res?

The logic can do a certain amount obviously, but I'm sure you could push it to the point of degrading performance - obviously there are limits. What we're wondering about here doesn't directly relate to the processing or bandwidth on the daughter die, though, but what happens when you need to start tiling. Or perhaps a combination of all of the above? (Although I can't see bw ever being an issue at least).

The reason for the suspicion about the lower resolution is that the res we've seen some shots at would allow the framebuffer to fit very neatly into the eDram without any tiling, and with 2xAA as required by MS (it comes to 9MB). It may all just be coincidence, but it seems a little odd. I'm trying to find out if 720p is the min native res, but to little avail sofar..

 

[Shifty Geezer]

Without any word on the logic circuits in eDRAM, what if, maybe, the logic isn't fast enough to provide AA & DOF & HDR & Motion Blur etc.?

I'm confused. AA is supposed to be on everything and it comes free, and I believed was instamatic with the hardware without the devs need ignt o do anything. Just like i can switch on/off AA on my PC's GPU, AA for XB360 is just switched on/off. If it's the 5% overhead as ERP says, can't that be easily compensated with a bit of texture reworking or something?

Definitely some unexpected information...

 

[Titanio]

To eliminate one thing - the cost of tiling to main memory bandwidth is only going to be the cost of writing out each tile once, correct? E.g. 14MB of bandwidth for 720p, 2xAA?

 

[Tap In]

MS stated all developers need to to make games that run at 720p and have 2xaa. ....

yep

I'm taking this article with a grain of salt.