[Pimp Racer]

Xbox360 “Xenos” compared to Playstation 3’s “RSX” – the GPUs:
Since the specs on the RSX are not fully known, I’ll only make comparisons on the solid aspects of the RSX that are unlikely to change from what Sony has reported at E3 2005 (unless they change for the better).

Unified Shaders vs Fixed Function Pipelined Shaders – the GPUs:
The general move to unified shaders was done after examining the hardware differences between the vertex and pixel shader pipelines. There was enough duplicate and similar hardware that unified shaders were favored and the pipeline differences were consolidated into one and the number of total pipelines increased.

The general trend/nature of computing hardware is that the more variety of code types the hardware had to handle, the more complex it gets in hardware, and it will run slower. This remains true with the pipelines of the RSX compared to the pipelines in the Xenos. A pixel shader pipeline in the RSX, at a one to one ratio with the abstract pipeline in the Xenos would perform faster, and the same thing in respect to the vertex shader pipeline. How much faster are the RSX fixed function pipelines individually when compared to a single pipline in the Xenos performing a specific task? I really don’t know and it depends on what that is to say which card has more shader horsepower.

It should also be noted that ATI’s current highest end video card, still sports a fixed function pipeline. This strongly suggests that unified shaders are not the way to go.
The above statement is under strict review and is likely invalid. Further discussion will ensue related to this topic in this thread. A revision change may be made later.

Xenos’ eDRAM:
On the Xbox360’s GPU, there are 10MB of eDRAM which provides an assortment “free” frame buffer effects such as anti-aliasing, alpha blending, and z-buffering. This daughter die is connected to the parent die with 32gb/s bandwidth, and has 256GB/s bandwidth between the eDRAM and the logic to perform the aforementioned operations. These operations are considered “free” with respect to bandwidth since they are performed by hardware and memory that isn’t shared by the rest of the GPU or CPU.

The exact nature of the AA advantage is 4xMSAA or 2xFSAA at 720p. Any larger or higher of a resolution and the 10 megabytes become insufficient to accomplish these tasks. The basic premise is that any operations that require a frame buffer of over 10MBs will make this eDRAM unavailable unless a tiling method is used for rendering. Examples of typical methods that increase are HDR(certain types)

The RSX doesn’t have anything to compare to this free bandwidth for anti-aliasing and other effects, but I don’t think Playstation 3 fans have to worry too much for a few reasons. First, even PC cards don’t sport eDRAM and AA still accomplished even with other effects enabled. Additionally, games can step up to 1080p on the Playstation 3 to lower the need for anti-aliasing. Lastly, this eDRAM is probably in the Xenos as a necessity rather than luxury, since the main memory bandwidth between the GPU and CPU on the Xbox360 is shared. The RSX and standard PC cards have dedicated bandwidth to video memory, which is definitely where the frame buffer resides.

The Cell Advantage:
The Cell will not, and should not be performing all rendering operations like the E3 2005 demos displayed. It should prove as very interesting that the Cell does perform well at those types of operations since rendering on a CPU offers more flexibility than vertex and pixel shader programs. It is unlikely the Cell would be processing the latter type of shader operation since it would involve the RSX processing an almost finished frame, before giving it up to the Cell, only for the Cell to send it back to continue down the graphics pipeline again with almost no work to be done.

Granted, 3D pipelines are configurable and you can speed up processing through it by disabling unnecessary features that you might have already accomplished on the CPU already. It is likely that developers will do some basic/macro level 3D operations on geometry before passing it off to the RSX to do more time consuming fine detailed processing.

The Xbox360 CPU could do the same thing too and aid in rendering task, but general purpose computing power doesn’t exactly lend itself well to the types of operations it would have to perform, and the vector processing capabilities of the Cell greatly out perform the Xenon in this respect.

Other Peripherals:
Hard Disc Drive:
In the case of the Xbox360, a 20GB hard drive is included in the premium version, and it is an upgradeable feature in the core version. Playstation 3 offers a 20GB hard drive on its “core” version, and a 60GB hard drive on its premium version. Advantages of a hard drive are generally well known to anyone who has a PC and has ever played a game for it. Both systems having a hard drive considered, there is nothing much to speak of except for the fact that you can get a bigger hard drive for the Playstation 3 if you are a person looking to store and playback larger amounts of media. It is likely both Microsoft and Sony will provide upgrades in the future.

The issue here is the fact that the hard drive is non-standard on the Xbox360. Some people get really defensive when this comes up. It is an issue that will and should be brought up since with the Xbox360 developers may not develop a hard drive feature they don’t feel enough consumers will see and enjoy. With the Playstation 3, developers know every consumer will have a hard drive and see the benefits of the feature they implemented.

It isn’t quite clear at this point though whether or not Sony is using a standard 2.5” SATA drive. If they are, then you could upgrade a PS3 hard drive as soon as any consumer SATA drive is released.

Optical Media Drive:
You know it was going to come up – Blue Ray vs DVD9. This isn’t really a fair versus. Blue-ray is superior to DVD9 in every respect. The only disadvantage Playstation 3 has in this respect is data reading speed. The 2x BD read speed is considerably slower than the 12x DVD read speed. The difference is between 72mbps vs ~130mbps, which in terms of common data rates known in the computer world are 8.6MB/s and 15.4MB/s. Should PS3 fans worry about their load times? I don’t think so as this is still higher than Playstation 2’s read speed, and since the hard drive is standard on Playstation 3, this will be large motivation for developers to use hard drive caching methods as a standard – not merely as feature.

The clear advantage of blu-ray is capacity and the possibility of playing the next generation standard for HD movie content. Blu-ray is looking good for becoming the next generation standard for movies as Hollywood has far more support for Blu-Ray than HD-DVD. If movie fans go where the movies are (which they will), then it will be blu-ray decisively. Playstation 3 is playing a part in getting consumers to match up with the studios by sporting a blu-ray player. Playstation 3 will probably be the majority of blu-ray player sales this year, and may even continue in 2007. That being said, it isn’t set in stone just yet so don’t hold your breath…

Capacity for games is where the bigger debate still exists with blu-ray and DVD9 with respect to the console wars. Will blu-ray be needed for this next generation? I can’t say it will be needed by any genre except any games that will decide to include HD FMV sequences on the media. But that is under the current way things are looking now. In a few years, or 5 years, that could all change and the space for blu-ray media is needed or wanted. Right now, you can’t make too strong of an argument for blu-ray being needed for the capacity of games, but it is an advantage.

Controllers:
Both consoles now sport pretty much the exact same button layout. All “who copied who”s aside, Playstation 3’s controller has motion sensitivity for better primary control in some game types, and a very large possibility to improve secondary control in all genres (i.e. tilting head around corners in an FPS, cameras, etc). Xbox360 has rumble feedback which was much enjoyed last generation, and PS3 fans will miss if it doesn’t come back (which it likely wont). Another significant difference is the pressure sensitivity of the face buttons. Playstation 2 had this, and Playstation 3 is most definitely going to include the same (it’s impossible to find out if it really is there or not). Xbox360, surprisingly, doesn’t do this even though the original Xbox controller did. Functionally, the major difference is merely that PS3’s controller has motion sensing.

Xbox360’s supports 4 RF(radio frequency) wireless controllers. Playstation 3 supports up to 7 wireless Bluetooth devices – not the keyword “device” as it means Sony isn’t limiting it to only controllers. Bluetooth notably has a shorter battery life due to its increased bandwidth capability although this shouldn’t be an issue as Sony’s controller appears to be using a built in rechargeable battery that charges through USB. Looking at the player number support, Playstation 3 has jumped to the lead over all other consoles this generation out of the box. Will you do 7 player multiplayer? Probably not split screen, 4 players is a comfortable maximum there, but for multiplayer games where the screen is shared and all players are on the same screen, 7 players is definitely feasible.

Bluetooth:
In reference to the last section – Playstation 3’s Bluetooth support is labeled with the word device as to be clear that it is not limited to controllers. This means that the Playstation 3 could utilize other Bluetooth devices on the market such as mice and keyboards. Bluetooth is basically aiming to be the wireless USB for computer equipment since RF devices are typically propriety end to end.

The Final Verdict?:
The Playstation 3 really does have a considerable hardware lead when it comes to games processing power. Despite Microsoft’s claims of the Xbox360 having more bandwidth, the evaluation brings in play numbers that make no sense to add up in the context of the “system” and throws in numbers which also shouldn’t be added together due to the buses being connected in series. Vector/SIMD/stream processing is very relevant and needed in games programming to achieve a lot of high end calculations that occur in games today.

Consider why a number of PC games in the past year or two have been tapping into the GPU hardware to get it to accomplish a few things. Consider why research has supported that GPUs are much faster than CPUs at performing many tasks that people though desktop CPUs dominated in. Consider why Ageia is proposing a new major piece of hardware on PCs to aid in processing physics in games. The answer is clear that a certain type of processing is needed, and it is not found in traditional desktop CPUs with general purpose processing power. Desktop CPUs are also not heading in a direction to ever compensate for these deficiencies either. If this post isn’t enough to convince you, you can go out and do research on the various topics yourself.

Microsoft has nice tools to help developers get the most out of Xbox360, which is a noble and needed effort for developing better games. But in the end, Xbox360 has a lower roof than the Playstatation 3, and over time the lead will show and be undeniable. Taste in games is purely subjective so I won’t say Playstation 3 will have better games as a whole, but they will be technically superior over time.
Playstation 3 and PC – Comparing and Contrasting:
Unlike consoles PCs are not static and evolve over time – or rather, the components of a PC evolve over time. In the case of a PC, CPUs, GPUs are the fastest evolving parts of it that are the most relevant to games processing. The downside to a PC is that is not purely a gaming platform and the CPUs are more general purpose in nature to handle code coming from an operating system running many applications at once. It has to perform integer math, floating point math, memory loading and storing, and branching all at an acceptable level of performance such that no area noticeably slows down processing. The other downside to PCs is that motherboards do not advance as rapidly and they represent some significant bottlenecks for PC games today. Here is a quick rundown of what is inside of a PC as it relates to game processing.

PC Architecture Summary:
PC Motherboard – AGP/PCI-E:
Motherboards dictate a baseline functionality limits you can get out of a PC. A motherboard is where you connect your CPU to the GPU, RAM, and other peripherals that connect to your PC. Because this is where you connect these components, it effectively sets the rate at which these parts can talk to the CPU*. If a motherboard uses AGP 4x, an AGP 8x card will be capped to communicating with the CPU at 4x speeds and the same goes to PCI-express.

To put some numbers on the speeds of these buses, AGP 8x runs at roughly 2GB/s peak bandwidth, and PCI-E runs around the same speed at 8x. PCI-E is however being upped to 16x which puts this speed at 4GB/s. If the graphics card and motherboard PCI-E or AGP speeds differ, the max bandwidth that can be obtained is the lower of the two speeds.

*On a PC, devices talk to each other through the CPU by sending signals (I think interrupts). The CPU in turn forwards or retransmits information to whatever the destination device is. On a PC, heavy bandwidth coming from the network to the hard drive, will have an impact on the CPU. On a console setup, this can be avoided as every byte transferred doesn’t actually have to take up cycles on the CPU.

PC Motherboard – RAM:
PCs today typically use DDR ram at varying clock speeds. The fastest variant of DDR RAM is DDR400 which runs at around 4GB/s in single channel mode, and 8.5GB/s in dual channel mode. DDR offers very low latency access to RAM which is important for desktop CPUs.

PC Graphics Cards:
Graphics cards are probably the single most important factor in determining the visual performance of games on the PC platform. PC games are typically the first to show the latest and greatest rendering methods and pushing certain features to the max due to hardware improvements that consumers can buy at a rate at which they please, and developers are free to use these expanded hardware features as they are released.

PC graphics cards also typically come with on-board memory so the GPU doesn’t have to gather resources through the slow AGP or PCI bus. PC graphics cards typically offer very high bandwidth to video ram since the video card manufacturer is completely in charge of building the link between the video ram and the actual GPU.