Interview w/ Matt Lee, MS ATG

[Nemo80]

I don't think the Cell is as well designed for game development as Sony would have you believe. Some aspects of the SPEs, such as the lack of branch prediction, make them particularly unsuited to running most game code, which contains a lot of branches. They appear to be designed more for serialized streaming math code, more common in video codecs and audio processing, the traditional domain of digital signal processing chips. The memory architecture of the SPEs, specifically their lack of automatic cache coherency in favor of DMA transactions, seems like a lot of overhead is needed to feed work units to the SPEs and copy the results back to system memory.

Well that's the usual bash. DeanoC already made clear that this is nonsense, and that development will lead towards SPE centric engines, with the PPE only acting in the background with basic stuff.
Branch prediction is something which none of the CPUs (Xbox or PS3) are made for. It simply has to be avoided.

The PPE appears to be essentially identical to one of the Xbox 360 cores, except without the VMX128 enhancements and with half the cache. However, a much greater assortment of work has to be crammed into this single core—all of the game loop, all of the rendering commands, and the system allegedly takes over some time as well. Only the second and third cores on Xbox 360 use a small timeslice to provide cool stuff like the Guide, music playback, Dolby Digital encoding, and more things that we can add in the future to all games, past and present.

Also marketing balbla. "Half the cache" yeah, but with much more cache per thread somehow he seems to forget. And he also forgets that the CELL PPE is an advanced version of those in the Xbox CPU which offers better multithreading performance.

And only the second and third cores on 360 use small timeslices for audio... ? wonder why some games use whole threads for XAudio...

I think porting from Xbox 360 to PS3 will be reasonably difficult, since the Xbox 360 has a lot more general purpose processing power that can be flexibly reallocated, and all of the Xbox 360 CPU cores have equal access to all memory. The asymmetric nature of the Cell could easily lead to situations where the game has too little of one type of processing power and too much of another. And the content might suffer as well, since you'll never see a PS3 title with more than 256MB of textures at any given time, due to the split graphics and system memory banks. When we announced 512MB of unified memory on Xbox 360, I think all of our game developers (and the artists too) did a little happy dance. It's easier to use and gives developers much more flexibility in how they allocate memory for various resources.

It will definately be diffucult - for Xbox 360. When extensive use is made of SPEs and BR disc there is only one way to handle this - downgrade grafics. He also claims wrongly that there cannot be more than 256MB of textures which is wrong as we already discussed here since textures can be streamed from XDR as well.

In terms of performance, I think that the PS3 and the Xbox 360 will essentially be a wash. We ran the numbers a while back and the two systems come up surprisingly close in theoretical peak performance, despite the one year difference in release dates. However, I know for a fact that we have a great advantage in software and services—our development environment and tools are years ahead of the competition, and this will ensure that Xbox 360 game developers can easily realize all of this performance and make superior games. Xbox 360 is a great system to develop on, a real pleasure—and I believe our developers agree.

And that's a LOL

Overall, he makes some nice technical comments to let some knowledge shine through and mixes them with marketing PR in order to look "professional"...

 

[Platon]

It will definately be diffucult - for Xbox 360. When extensive use is made of SPEs and BR disc there is only one way to handle this - downgrade grafics. He also claims wrongly that there cannot be more than 256MB of textures which is wrong as we already discussed here since textures can be streamed from XDR as well.

That will also depend on marketshare and what will be the leading development platform for the developers...

 

[Shifty Geezer]

Hmm, where did he say this.

The interview points out that the SPE's aren't good for most tasks, PPE is like a single XeCPU core but not as good, the PS3 can't use as much texture space so won't look as good...doesn't that amount to 'PS3 isn't as good as XB360'? I agree with rabbidrabbit's assessment of MS's PR tactics. On the one hand they say XB360 is better designed, right back from E3 '05 when they have 3x the interger perforamnce, and integer performance is 80% of games, type comments. And then they say the two systems are very comparable. If all their tech-breakdown were valid, XB360 should be to PS3 what XB was to PS2.

As for validity of real tech insight, just take a ganders at a comment like this...

The memory architecture of the SPEs, specifically their lack of automatic cache coherency in favor of DMA transactions, seems like a lot of overhead is needed to feed work units to the SPEs and copy the results back to system memory.

Oh no! The SPE's have to copy data from main RAM into local storage to use it, and then having done the work, have to copy it back again to main RAM! How rubbish is that?! If only they worked directly in super-slow main RAM so they didn't have the overhead of having to copy the databack and forth. Or maybe they should use a cache, which gets over this problem by copying the data from main RAM to a fast local storage, using it there, and then copying it back again. Um, hang on...

Any hardware spokesperson for one of these companies is going to be interviewed with an agenda to promote their company's system, and any cross-platform talk should be ignored. sonyps35 shouldn't have quoted this part of the interview as we all know it's useless. The juicy part isn't this bit quoted unless you like mindless gossip. The juicy part is talk of how they deal with multithreading etc. - the real bits of info given to describe the aspects of working with their own hardware.

 

[MightyHedgehog]

I honestly don't know why you guys get so flustered over this stuff. If it were a Sony tech guy in the interview, the answers would be a volley from their side of the fence...praising their own hardware and software, etc.

 

[Farid]

Are some of you guys discussing generic claims about Cell, a Sony product, made by a MS developer? Why?

You guys should discuss the rest of this interview, like the parts where the interviewer asks about Lee's everyday life at ATG, what sort of games he likes, what he hates/likes about his job, or how many X360 he thinks MS can sell to retailers these holydays...
And, of course, we also get to learn that the third party developers mostly ask technical questions to the developer support group.

The 3/4 of the interview are a waste of internet space and the remaining 1/4, about the X360 technology, brings nothing new to the table.

Sadly, M.Lee did seem okay to talk about the XDK tools, like PIX, but the interviewer thought that asking something like will the developer get more comfortable with concurrent thread models was far more important than expanding the discussion about what is the best performance evaluation tool on the market (PS3 devs would kill for something that is 10% like that, just FYI).

 

[Crossbar]

I honestly don't know why you guys get so flustered over this stuff. If it were a Sony tech guy in the interview, the answers would be a volley from their side of the fence...praising their own hardware and software, etc.

I think you are right, a Sony spokesperson would probably spend about the same amount of BS about their competetitor but it would also likely result in about the same type of replies at this forum.

Matt seems to be a reasonably nice guy. I think the download in the background feature sounds nice. I wonder if it will be as easliy to implement such a feature on the PS3. On the 360 the games cannot rely on having a HD to stream data from, while a game on the PS3 could possibly do that. If you are downloading a movie at the same time the search times may increase significantly.

 

[TurnDragoZeroV2G]

Meh on the PS3 aspects of the discussion, both in the article and here, but especially here.

The rest of the interview was nice and interesting, but I agree that Dave needs to get on the phone and get a graphics-oriented interview soon!

 

[LunchBox]

The only thing that irked me from this interview is that he easily claimed 6 hardware threads for the system when you don't get 6 equal threads all the time due to context switching. Didn't MIcrosoft even suggested that the other "lesser" thread be used as a helper thread? It seemed more like PR than a technical interview. I'm also quite curious if he is working with a PS3 dev kit, and if he's had first hand work done with them, since he's quite sure of his answers. But I like the guy, since he ported dope wars to palm

 

[one]

Anything is better than nothing, I welcome all PR or whatever as long as they are out of the horse's mouth, they are at least, but marginally, more valuable than PR by unpaid fanpersons

As for the interview, this part is interesting,

Right now, the best example of using procedurally-generated worlds is a third-party bit of middleware "SpeedTree," which was used to generate all the trees in Oblivion, although this was not done on the fly. This cuts down a lot of work for the artists, who then don't have to spend days making dozens and dozens of slightly different tree models. The idea of using on-the-fly procedural synthesis is one that even Microsoft hasn't explored yet.

It confirms what I read on a thread in this forum, that they are not yet using on-the-fly procedural synthesis which was featured in an old Arse Technica article in a big way and in the mouth of J Allard several times. So the "With 96KB .kkrieger we don't need Blu-ray, DVD is just enough!" argument is out of consideration right now. Not sure if it's because of performance limitation or difficulty in getting quality results though.

 

[TurnDragoZeroV2G]

IIRC, those kkrieger demos were never on-the-fly. All of them decompressed prior to running. Perhaps I misunderstood what you were trying to say, though.

As for the threading, helper threads are pretty much a suggestion to keep things simpler. It's not the optimal situation, just like assigning Xenon cores and SPUs to specific tasks aren't the optimal use of them.

 

[Platon]

It confirms what I read on a thread in this forum, that they are not yet using on-the-fly procedural synthesis which was featured in an old Arse Technica article in a big way and in the mouth of J Allard several times. So the "With 96KB .kkrieger we don't need Blu-ray, DVD is just enough!" argument is out of consideration right now. Not sure if it's because of performance limitation or difficulty in getting quality results though.

As TurnDragoZeroV2G pointed out I think that they are refering to two different things. In those proceduraly generated games, like kkrieger, all the textures, geometry and everything else proceduraly generated are created upon start up, or the "loading" part of the game. I would assume that what he is talking about here would be to do that kind of thing during gameplay as well, without having to load, but creating those textures/geometry during gameplay, in the same way that you now can have decompression going on in the backround.

Then you have of course the oblivion case were you use procedural synthesis during the creation of the game which just creates normal assets in the end...

 

[one]

IIRC, those kkrieger demos were never on-the-fly. All of them decompressed prior to running. Perhaps I misunderstood what you were trying to say, though.

Well I'm not the one who brought .kkrieger into the discussion, please search this forum for related discussions about the need of Blu-ray, someone who said next-gen games wouldn't need Blu-ray pointed me to .kkrieger.

Considering that the guy refers to SpeedTree use in offline content creation, I think everything except for offline generation is categorized as "on-the-fly" by him. It means procedural synthesis that is not on-the-fly doesn't save the disc space of distribution media. OTOH, for on-the-fly procedural synthesis, you put only a seed and an algorithm on a disc.

 

[TurnDragoZeroV2G]

I'm not sure... well, just to clarify, as far as I know (may be some ass/u/m(e)ptions here)

On the fly would be having Xenon generate spheres and more complicated geometry data from higher order equations, storing in locked L2, and have the GPU consume this data. Or creating a texture in the same manner (but, according to dev comments, far, far less feasible and probably not worth it).

On load-time would be what kkrieger does; what you would do if you wanted such extreme compression for a disc, which seems to be the source of the argument you're referring to. Trade a minute or two of load time for getting more content onto a smaller disc. I don't see how anything in this interview negates that in any way. From the context, it seems clear, if not probable, that on-the-fly refers to what was discussed in the referenced articles for that question, outlined above (from what I remember, that is).

Then offline, precomputed stuff such as was used in Oblivion.

 

[Powderkeg]

I think you are right, a Sony spokesperson would probably spend about the same amount of BS about their competetitor but it would also likely result in about the same type of replies at this forum.

Not a chance.

This forum is clearly slanted towards PS3 bias. If you think people would make the same type of replies here if it were an interview with a Sony rep then I would like to point you to these threads:

http://www.beyond3d.com/forum/showthread.php?t=31307
http://www.beyond3d.com/forum/showthread.php?t=31307

Here we have a similar interview with a high profile Sony rep. He hypes his product as being the greatest thing since sliced bread, he takes several passing digs at the competition, and there is near universal praise from forum members here for what he says, and much discussion about how smart all of his plans are.

Not one person comments about how his comments are just PR talk, or says anything against him for his little digs at the competition.

One thing this forum is not is fair and balanced.

 

[one]

Not one person comments about how his comments are just PR talk, or says anything against him for his little digs at the competition.

Oh, really? He's quick in the 6th post in the thread.