PS4 For Dummies
February 22, 2013 4 Comments
I’ve seen some confusion about the PS4 specs, lets see if we can get some order out of the chaos.
These are the official specs released and as the small note at the bottom says, subject to change without notice.
The RAM Question
People have falsely claimed that the PS4 features 8GB of graphics RAM (video RAM, vRAM). I’ve seen the 8GB RAM compared to the new nVidia Titan card with 6GB.
This is an incorrect interpretation, the PS4 features 8GB of GDDR5 RAM which is a type of RAM used today in high-end video cards. It is however NOT the total available graphics memory for graphics processing. The 8GB GDDR5 RAM is shared with CPU operations (even though SONY was very careful to avoid the word “shared memory” in this context)
A typical gaming PC today has 4-8GB of DDR3 system RAM and additionally features vRAM on the graphics card itself. Typically this is 1-4GB with current mid-high range GFX cards and the nVidia Titan at 6GB.
So a typical gaming PC can have 5-12GB of total RAM between CPU and GPU, the PS4 has 8GB.
Are higher numbers for the RAM-type better (DDR3 vs GDDR5)?
Yes and no, it depends on the system architecture as well as RAM-type.
DDR-type RAM is generally optimized for CPU operations and architecture, GDDR-type RAM is optimized for GPU (Graphics Processing). Were I to use GDDR5 RAM for CPU operations in a standard PC (hypothetically), I would notice increased latency. Were I to use DDR3 RAM for GPU, the same applies.
So a higher number behind the DDR (Double Data Range architecture) is not immediately indicative of “better”.
Benefits Of Shared RAM in the PS4 (speculation)
The benefit of shared RAM in the PS4 could be a wider flexibility and dynamic access to memory. For example, a game might not use a lot of CPU-bound RAM for general purpose operations like AI, this means that more RAM can be assigned to graphics processing and produce higher graphical fidelity (higher resolution textures). Or, vice versa, if the game is not very graphics-RAM intensive, the PS4 can allocate more RAM to CPU operations. Games could benefit from this massively as this isn’t possible with a standard PC, you either have just enough, or you have too much of something.
An RTS traditionally has lower memory requirements on the graphics side as the main focus is large scale engagement, but requires more memory when it comes to AI and keeping track of actors as well as things those actors do. On a mid-range PC we often experience “bottlenecking” in either CPU or GPU. A relatively popular example is Mount And Blade which uses primarily CPU power as well as system RAM but GPU and vRAM is relatively underutilized.
The PS4’s shared memory architecture could conceivably prevent such bottlenecks.
As noted before, GDDR5 RAM was never used in conjunction with a CPU architecture before and we don’t really know how this can or will impact performance. Standard components in PCs, and with it the x86-64 AMD chip in the PS4 are not made to handle DDR5 so we have no data on how this will work performance-wise.
DDR3 and GDDR5 are very different and some of the things are very technical like bus-type, bus-speed, clock, transfer bandwidth, etc, but we can’t expect that both CPU and GPU will be using the same configurations for these things. i.e. there might be a situation where the DDR5 was adapted primarily for GPU performance but will under-perform with CPU operations, or vice-versa.
There is a reason why PCs have dedicated components for CPU and GPU and why on-board video cards tend to suck badly.
There isn’t really much to say here except that the PS4 finally decided to use x86 architecture which is the current standard PC architecture. The PS3 in comparison uses cell processors that are not compatible with x86 system architecture, which leads to problems when porting games to the PC (or XBOX 360).
8 cores are good and they are not shared with the GPU which is also good, this makes the PS4 a bit of a beast when it comes to CPU power (compared to the current gen). Current gaming PCs often feature 4-6 cores (core i7, etc) but 8 core processors are available to the public at a price. CPUs are hard to compare as the amount of cores isn’t the only measure of their power. Parallel processing is good but clock speeds are important, as well as L(X) cache, buss-type and access times. We have no information about those, the Jaguar is not currently available for consumers.
Needless to say, current-gen games utilize little to none of that CPU power the PC boasts as most games are designed for the (now old) 360 and PS3.
Another curiosity is that CPU and GPU are integrated, they are an APU, which has its own problems.
We also unfortunately have no precise information about the GPU core and chip.
All we know is that it boasts 1.87 TFLOPS which would put it close to a AMD Radeon HD 7850 (1.7 TFLOPS) which is a higher-end GFX card available to the public. It’s a good card but already a year old (and will be 2 years old when the PS4 actually gets sold to consumers).
Compared to that, the Nvidia GeForce GTX 690 boasts 5.6 TFLOPS, close to 3x the processing power of the Radeon 7850.
Yet again, a direct comparison of GFX cards and GFX power is not really possible as it all depends on architecture. The Radeon 7850 comes with 2GB of vRAM stock for current PCs, but the PS4 can conceivably utilize a lot more. In comparison the GTS 690 comes with 4GB vRAM stock. The question is, even if we say that the PS4 would allocate 4GB at any given time, would the 1.87 TFLOPS be enough to actually process all this available data?
Looking at the stock cards I would say no. Just slapping more RAM onto something isn’t enough to make it better. If we look at the HIS Radeon HD 7850 4GB iPower IceQ Turbo, which has 4GB integrated RAM, we notice barely any improvement in performance (http://www.guru3d.com/articles_pages/his_radeon_7850_ipower_iceq_4gb_review,1.html). It’s a great card, don’t get me wrong, but it could bottleneck the system.
It’s a curious choice to feature this flexible an architecture with this powerful a CPU and shared vRAM if the GPU won’t be able to process it.
In conclusion I think that the PS4 will realistically not assign more that 2GB to the GPU, leaving 6GB for CPU purposes. All those social and connectivity features take RAM as well, even with a dedicated chip handling the processing in the background. Not to mention that a large chunk of RAM will probably be used for the on-the-fly video recording feature that has been demonstrated.
Developers will need to take this into consideration when coding their games, they can’t just assume all the 8GB will be available to them at all times. On a PC we are relatively used to turning off unnecessary programs when we are gaming but a console can not expect the consumer to switch off his ustream because Killzone suddenly dropped 10FPS. If the feature set doesn’t work with “everything on max” it doesn’t work period.
Ultimately the enemy of all consoles is Moore’s Law. If processing power doubles every two years, your console is twice as shit two years from now (hyperbole).
Similarly the PS4, when it finally gets released at the end of 2013, will feature static technology that will already be obsolete. Let us all hope that the next-next-next gen development-cycle will be shorter than the 8 years of software-stagnation we have experienced.