Microsoft's Xbox 360, Sony's PS3 - A Hardware Discussion
by Anand Lal Shimpi & Derek Wilson on June 24, 2005 4:05 AM EST- Posted in
- GPUs
Final Words
Game consoles have always been different, architecturally. The PlayStation 2 was very different from the original Xbox, and thus it is no surprise to see that the two platforms continue to be quite different this time around.
Given what we’ve discussed thus far, there are a number of conclusions we can draw:
The most important thing to keep in mind is that the revolution in physics engines and collision detection isn’t going to happen over night. The first games for both consoles will, for all intents and purposes, be single threaded titles. More adventurous developers may even split up execution into two concurrent threads, but for the most part don’t expect to see a dramatic change in the quality and reality of the physics simulation of the first titles, especially when compared to titles like Doom 3 and Half Life 2.
However, a change is coming and by the end of next year multi-threaded game engines should be commonplace on both consoles and PCs, which will hopefully lead to much more entertaining experiences. The approach to that change will be different according to the platform; without a doubt, developers will have their work cut out for them.
The transition to multi-threaded development alone will increase development time 2 or 3 fold. Not to mention that the approach to architecting game engines will differ whether you are porting to the Xbox 360 or the PlayStation 3. The Xbox 360 is clearly going to be the easier of the two to develop for once a game engine is multi-threaded, just because of the general purpose nature of its hardware. That being said, it won’t be impossible to get the same level of performance out of the PS3, it will just take more work. In fact, specialized hardware can be significantly faster than general purpose hardware at certain tasks, giving the PS3 the potential to outperform the Xbox 360 in CPU tasks. It has yet to be seen how much work is required to truly exploit that potential however, and it will definitely be a while before we can truly answer that question.
Cell’s on-die memory controller is a blessing for game performance; it most definitely will keep the PPE fed far better than the Xbox 360’s external memory controller. Even the cache size advantage of the 360 won’t be able to offset the reduction in memory latency thanks to an on-die memory controller.
The on-die memory controller is not all an advantage however, a big part of its inclusion is out of necessity. Remembering back to our discussion about the SPEs as being in-order with no cache, threads run on these processors only have access to 256KB of local memory, which is reasonable for a cache, but not much in the way of memory. So these SPEs will depend on having low latency access to memory in order to keep their pipeline filled and actually contribute any useful performance to the system.
At the end of day 1, when running mostly single threaded code, the performance difference from a CPU standpoint between the Xbox 360’s Xenon and the PS3’s Cell processor is basically a wash. The 360 has more cache, while the Cell has a lower latency path to main memory. In the end, the first generation or two of games will mainly be a GPU battle between the two consoles, and both will offer significant improvements over what we have with current consoles.
Graphics-wise the 360’s Xenos GPU and the PS3’s RSX are fairly different in implementation, but may end up being very similar in performance. Treating Xenos as a 24-pipe R420, it could be quite competitive with a 24-pipe RSX despite a lower clock speed. The unified shader architecture of the Xenos GPU will offer an advantage in the majority of games today where we aren’t very geometry limited. The free 4X AA support offered by Xenos is also extremely useful in a console, especially when hooked up to a large TV.
If the PS3’s RSX isn’t much more than a higher clocked G70 then at least we have a good idea of its performance. NVIDIA has mentioned that by the time the RSX launches we will have a faster GPU on the PC, which leads us to believe that the performance advantages of the RSX are mostly clock speed related. At 550MHz, the RSX GPU should have no problems handling both 720p and 1080p resolutions, although the latter won’t be possible in all games, mainly those that are more texture bandwidth bound. We do think it was a mistake for Microsoft not to support 1080p, even if only supported by a handful of games/developers. At the same time, by not imposing strict AA implementation regulations like Microsoft, Sony does open themselves up to having some PS3 games plagued by jaggies despite the power of the console. Given the amount of power in both of these consoles, we truly hope that their introduction will mark the end of aliasing in console games, but some how we have a feeling it won’t. Aliasing has plagued console games for too long for it to just disappear, that has to be too good to be true.
With at least 5 months before the official release of Microsoft’s Xbox 360, and a number of still unanswered questions about the PlayStation 3, there is surely much more to discuss in the future. The true nature of NVIDIA’s RSX GPU, the real world programming model for Cell, even final hardware details for both consoles has yet to be fully confirmed. As we come across more information we will analyze and dissect it, but until then we hope you’ve gained more of an understanding of these consoles through this article.
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jotch - Friday, June 24, 2005 - link
#20 well that can't be right for the whole consumer base, as I'm 24 and only know other adults that have consoles and alot of them have flashy tv's for them as well, I do. I think if you look at the market for consoles it is mainly teens and adults that have consoles - not kids. Alot of people I know started with a NES or an Atari 2500, etc and have continued to like games as they have grown up. Why is it that the best selling game has an 18 rating?? (GTA: San Andreas)The burning of the screen would be minimal unless you have a game paused for hours and the tv left on - TV technology is moving on and they often turn themselves off if a static image is displayed for an amount of time. So burning shouldn't occur.
nserra - Friday, June 24, 2005 - link
All the people that i know having consoles is kids (80%), and their parents have bought an TV just for the console, an 70€ TV.....Who is the parent that will let kids on an LCD or PLASMA (3000€) to play games (burn them).
Or there will be good 480i "compatibility" in games, or forget it....
#17 I agree.
fitten - Friday, June 24, 2005 - link
#14 There are a number of issues being discussed.For example, given the nature of current AI code, making that code parallel (as in more than one thread executing AI code working together) seems non-trivial. Data dependencies and the very branch heavy code making data dependencies less predictable probably cause headaches here. Sure, one could probably take the simple approach and say one thread for AI, one for physics, one for blah but that has already been discussed by numerous people as a possibility.
Parallel code comes in many flavors. The parallelism in the graphics card, for instance, is sometimes classified as "embarassingly parallel" which means it's trivial to do. Then there are pipelines (dataflow) which CPUs and GPUs also use. These are usually fairly easy too because the data partitioning is pretty easy. You break out a thread for each overall task that you want to do. You want to do OpA on the data, then OpB, then OpC. All OpB depends on is the output data of OpA and OpC just depends on OpB's final product. Three threads, each one doing an Op on the output of the previous.
Then there are codes that are quite a bit more complex where, for example, there are numerous threads that all execute on parts of the whole data instead of all of it at once but the solution they are solving for requires many iterations on the data and at the end of each iteration, all the threads exchange data with each other (or just their 'neighbors') so that the next iteration can be performed. These are a bit more work to develop.
Anyway, I got long-winded anyway. Basically... there are *many* kinds of parallelism and many kinds of algorithms and implementations of parallelism. Some are low hanging fruit and some are non-trivial. Since I've already read that numerous developers for each platform already see low hanging fruit (run one thread for AI, another for physics, etc.) I can only believe they are talking about things that are non-trivial, such as a multithreaded AI engine, for example (again, as opposed to just breaking out the AI engine into one thread seperate from the rest of game play).
probedb - Friday, June 24, 2005 - link
Nice article! I'll wait till they're both out and have a play before I buy either. Last console I bought was an original PlayStation :) But gotta love that hi-def loveliness at last!#3 yeah 1080i is interlaced and at such a high res and low refresh the text is really difficult to read, it'd be far better at 1080p I think since that would effectively be the same as 1920x1080 on a normal monitor. 1080i is flickery as hell for me for desktop use but fine for any video and media centre type interfaces on the PC.
A5 - Friday, June 24, 2005 - link
You know, the vast majority of the TVs these systems will be hooked up to will only do 480i (standard TV)...jotch - Friday, June 24, 2005 - link
#14 - here here!jotch - Friday, June 24, 2005 - link
#10 - sounds to me like they're way ahead of they're time, future-proofing is good as they'll need another 6 years to develop the PS4 - but the Cell and Xenon will force developers to change their ways and will prepare them for the future of developing on PC's that eventually have this kind of CPU chip design (ref intel's chip design future pic on the first page of the article), like the article says the initial round of games will be single threaded etc etc...You might get alot of mediocre games but then you should get ones that really shine bright on the PS3, noticeably Unreal 3 and I bet the Gran Turismo (polyphony) guys will put in the effort.
Pannenkoek - Friday, June 24, 2005 - link
I'm quite tired of hearing how difficult it is to develop a multithreaded game. Only pathetic programmers can not grasp the concept of parallel code execution, it's not as if the current CPU/GPU duality does not qualify as one.knitecrow - Friday, June 24, 2005 - link
you'll need HDD for online service and MMOPhow many people are going to buy a $100 HDD if they don't have to?
LanceVance - Friday, June 24, 2005 - link
"the PS3 won’t ship with a hard drive"If that's true, then will it be like:
- PS2 Memory Card; non-included but standard equipment required by all games.
- PS2 Hard Drive; non-included and considered exotic unusual equipment and used by very few games.