Head to Head:
Bandwidth Assessment:
If there was a diagram showing PC motherboards compared to the bandwidth diagram of the Playstation 3, you might be shocked to see some of the narrow bandwidths provided in PCs, but you’d also notice that the bandwidth provided in top end graphics cards today are already around double the currently known bandwidth for the RSX and Xenos to video memory. A top end GeForce or Radeon card has around 50GB/s bandwidth between the GPU and its video ram, while the RSX only has 22.4 GB/s. This factors in greatly with the texture detail displayed on PC games as compared to those in console games. On a PC, you can push higher quality textures onto your polygons, and use bandwidth expensive filters liberally with this added bandwidth. Many games enable these features and it isn’t even significantly necessary for the game’s visuals, or it could easily be compensated for using cheaper methods.
Comparably, PCs use an AGP or PCI-E bus for CPU to graphics card (memory or GPU) communication. It is extremely low at 8GB/s on the top end (PCI-E 16x). On a PC, it is safe to say that the graphics card will not put video memory that’s needed frame by frame, on the CPU’s main memory with such a slow link. The Playstaiton 3 sports a link of 35GB/s bandwidth between its CPU and GPU alone to allow them to work together to accomplish tasks without going through a huge bandwidth bottleneck. It effectively allows the RSX to not be excluded from the 256MB XDR RAM if it needs extra video memory.
PC CPUs also have much lower bandwidth to RAM compared to the Playstation 3. Today the fastest(common) RAM on desktop PCs runs at 4GB/s, and a gaming rig might try to setup dual channel upping this bandwidth to 8GB/s. On the PC end this bandwidth is so low due to the fact that general purpose computing generally doesn’t have a demand to transfer or process massive chunks of data at such a fast rate. For PC games, this does put a limitation on games that might want to process massive amounts of data on the CPU. PC games just don’t do this type of thing.
CPU performance:
On that note, CPUs on PCs are general purpose CPUs. The mainstream ones are all x86 based and are scalar processors – meaning they execute one operation at a time (on a single pipeline per core) on one piece of data. General purpose CPUs have gotten extremely fast at executing ALU related instructions, but this improvement has not been kept up with by memory(RAM). Due to this, a large part of die space is taken up by hardware aimed to hide general purpose CPU access times. This added hardware dissipates a lot of heat and lowers the overall efficiency of the CPU to keep it running fast. This hardware is needed in the general purpose computing scene since random accesses to memory are frequent due to application switching, and even a single application has many random variables to keep track of in memory. This need however, is not needed as much for games and the extra hardware would be a much greater waste of space and power. I already mentioned the lack of need for general purpose computing power in the Xbox360 contrasting so I won’t mention it again from a software standpoint.
Intel/AMD are the primary manufacturers of desktop CPUs today and all have huge amounts of die space allocated to general purpose computing. However, to not be completely outdone by the world of SIMD processing, MMX, 3DNow!, and SSE technologies were added to these general purpose CPUs to improve their 3D gaming and multimedia functions. These SIMD instruction sets and hardware associated with them are still behind the single VMX-128 instruction set and hardware included in the Cell’s PPE as they only have 16 registers as opposed to 32. SSE only recently supported operations that apply between elements in the same vector register with the latest version SSE3, although 3DNow! had this functionality from the start. MMX and 3DNow! also shared registers with the x86 floating architecture at the start which meant they couldn’t be executed simultaneously with x86 floating point code(x87). Since then, this may have changed though.
SSE, MMX, 3DNow! don’t even begin to scratch the power offered on a single SPE on the Cell. Not to mention the Cell has 7 of them in addition to the VMX-128 instruction set. For games processing, Intel/AMD CPUs are vastly outdone, and they will not be catching up this generation or the next. Buying newer and newer CPUs will not increase PC gaming performance drastically, and they won’t be catching up to the Cell for a long time.
Graphics performance:
In purely assessing the graphics cards compared the RSX, the RSX likely doesn’t weigh in along side of the heaviest hitter today. As I said before in the bandwidth assessment, graphics cards have extremely high bandwidth between video RAM and the graphics rendering pipelines that make up the GPU. The bandwidth and processing capability in graphics chips increases quickly as new cards are released on the market, which is about 3-4 per year, and a new generation adding more filters, methods, or effects every year. Consoles are quickly outdone in the eyes of PC game developers in the graphics department. When you see the latest top-end PC game, remember that it’s running on the latest top-end graphics card, and in some cases, these games are targeting cards that aren’t going to run well until the next generation of graphics cards is released.
The “Cell factor” added into graphics processing should also be considered in boosting the visuals of Playstation 3’s graphics when compared to PC games. Unlike a desktop CPU, the Cell is actually equipped to process many of the tasks that are performed on a graphics card, and there is enough bandwidth between the Cell and RSX so they both can render graphics. The most obvious approach to getting more out of the Cell is using it to do hardware transform and lighting (T&L), and other basic or complex vertex operations that a vertex shader might do. Upon entering the geometry to the GPU, a developer would disable these rendering steps since they have been performed already and it goes through these stages on GPU’s rendering pipeline quicker, giving it more time to accomplish something in another stage like pixel shading, AA, or HDR. There is actually feasible bandwidth for pixel shader operations to be done on the Cell before it is handed back to the RSX to do nothing but move it to the frame buffer and send the output signal to the display.
How much processing can be done on the Cell to make up for the PC graphics card advantage? I can’t answer that well since GPU specs and statistics are usually documented in results with little introspection as to what hardware does what, and how quickly it is doing it. If anyone knows a bit more about this, it would be a good area to get into deeper discussion with. I am pretty confident that the Playstation 3 with the Cell + RSX working together can look on par with many PC games that will be released in 2007.
One thing that the Playstation 3 developers couldn’t easily make up for is the bandwidth limitations of the RSX. No matter what, the RSX is limited to its 22.4GB/s link to GDDR3 RAM which limits the rate large textures can be rendered, which couldn’t be made up by Cell’s processing power. The wildcard in this scenario is obvious if you look at the RSX/Cell diagram and remember that RSX has full access to the Cell’s 256 MB/s of XDR RAM. The channel would first have to go through the Cell’s 25.6GB/s link to RAM, then the Cell/RSX link at 35GB/s – limiting bandwidth being the 25.6GB/s. If this RAM could be used simultaneously with the GDDR3 RAM, then the total peak bandwidth with memory that the RSX can use is 48GB/s through two buses, which is still on par with high end graphics cards today.* Do note that this scenario drains the Cell of all bandwidth to XDR RAM while the bandwidth is being used. This could be a non-issue by the nature of a game loop since the CPU is less likely to need such high bandwidth to RAM during rendering stage of a game loop.
Even if the 48GB/s bandwidth on the RSX is on par with top end PC cards today such as the GeForce 7900GTX or the ATI X1900 XTX, that number is static. Next year graphics cards could (and likely will) be sporting bandwidth figures in excess of 70-80GB/s.** They will push larger and more detailed textures faster than what 48GB/s can do, and will eventually have execution speeds that the Cell’s processing will not be able make up for.
*In a press interview with the Heavenly Sword developer(Ninja Theory) a few weeks ago, this idea was hinted on. I believe a developer said something about the RSX having two buses to memory and not just one. This very well could be what he was referring to without getting into the details.
**After I wrote that, I looked up the bandwidth on the GeForce 7950GX2 and see that it has 76.5GB/s bandwidth to video RAM. Next year’s bandwidth for top end PC graphics cards are looking to get up to 150GB/s or more bandwidth at this rate.
Frame-rate:
Frame rates vary for a number of reasons. It actually factors in considerably in the visual department because smoother and stable frame rates look better. While 30 FPS is well-playable, 60 FPS at the same visual quality will just make the game feel much better.
The reason why I mention this here is that PC games typically showcase very unstable frame rates. Unless your PC is far beyond the recommended requirements of a game, you will probably notice that most games have frame rates dropping to around 10-15 in certain parts, and going up to 30 or more during others. I’m not completely blaming this on developers since they have a lot of different hardware to worry about, but it is something that degrades the overall pleasure of playing a game. Playstation and Nintendo (sorry, Xbox360 and original have shown some awfully ugly frame rate drops similar to those seen on PCs), have historically shown games with less frame rate variation.
Controllers:
Mouse and Keyboard vs Playstation 3 controller. When it comes to RTS and FPS games, then Playstation 3 is owned along with every other console. Playing these types of games on the highest multiplayer tiers will always yield better players on the mouse + keyboard combo. That being said, the controls can still work on the Playstation 3, and players can get relatively good.
For many other game types, a PC keyboard and mouse suffer almost like a console controller does with RTS and FPS. You’d probably want a PC gamepad or joystick to play flight sims, fighting games, racing games, sports games, and probably more. The problem with a PC is that these things aren’t standard and not every developer will care to put in rumble features or motion sensing features even if they are out for certain PC gamepads on the market. The number of buttons supported on a decently programmed PC game does scale accordingly though to whatever the user has. PCs are lagging behind in the pressure sensitivity department and I don’t even think DirectX supports detecting pressure on button presses unless they’ve actually updated it since DirectX8(fyi, DirectX9 still used the DirectInput8 API).
OMG Look at Crysis!!!:
Yeah, this game got its own section due to how much it has annoys me on these forums. It is always being compared to the abilities of the next generation consoles processing abilities as it if is some unattainable goal for consoles.
Guess what is responsible for those graphics? I’ve already said it and you probably already know it if you’ve read and understood everything I wrote so far – top end graphics cards. Can the RSX beat it alone? I might lie to you and say “yeah it can do that” and fail to mention the RSX would likely be running at 5 frames per second if it did - as would any comparable PC graphics card would too. But I’d rather try to be a bit more honest than what nVidia would tell you. In order for the Playstation 3 to match or surpass those visuals, the Cell would have to be used to handle some of the parts of the 3D rendering pipeline to speed up rendering through the RSX to levels which could probably even exceed what Crysis looks like. Of course, at some point in the future when GeForce 8950GTX-SLIs come out, you could probably run Crysis at ridiculously high 16xAA, 16xAF, FP32 HDR and what have you settings, but those are just polish related visuals, not the baseline visuals that are a large determinant of what makes games look good.
Short story is that you won’t be disappointed with the Playstation 3’s visuals. It will be quickly outdone by PC graphics cards in terms of the nitty gritty technical settings like AA, HDR, AF, and shader model version whatever. Don’t let that discourage you because artists and improved techniques on the Cell + RSX will make the improvement of Playstation 3 visuals keep up even if it isn’t displaying more polygons with higher settings.
The Final Verdict?
While PCs GPUs are evolving and pushing the visuals beyond consoles due to new graphics card hardware being released yearly, the rest of the PC world is relatively static and offers little to no improvement when it comes to gaming. When multi-core CPUs hit the shelves for desktop PCs, there could be an increase in performance for games and more tasks being done on the CPU, but no more than what Xbox360 has or will show us with its 3 cores.
All of the next generation consoles already possess more games processing power than PCs with their increased and improved SIMD units. Unfortunately, developers aren’t taking the best advantage of this extra power in most cases as writing computational code for games is more difficult than the direct logical approach. Multiplatform development will be the biggest inhibiter of the Playstation 3’s potential.
PCs gaming or PS3 gaming doesn’t really have a clear technical winner. PC’s constantly evolve so in some aspect they will always be better for graphics when you always have the top end graphics card. The Playstation 3 will offer more flexible computational power that can be applied to more accurate physics, sound, or other computational related tasks than a PC. PS3 cannot catch up graphically which seems to be the most important or obvious difference between games. But PCs will not catch up in physics processing and other computational simulations unless the physics card catches on and is integrated well.
TAKEN FROM HERE ALL CREDIT TO THIS SITE!
http://ps3forums.com/viewtopic.php?t=27123
BTW this took me over 20 mins just to copy and paste! ARGH!!!
