Sony’s Playstation 4 is pretty infamous by now for its memory system. The Playstation 4 sports 8GB of GDDR5 memory, giving a total bandwidth of 176GB/s of unified memory, with a robust bus structure to help send data whizzing around the system.
The Playstation 4 wasn’t always planned to have 8GB of RAM however. Indeed, until very much near the launch of the machine, developers had all assumed and were told that 4GB of GDDR5 was what Sony were targeting. This is back when the machine was codenamed ‘Orbis’ and the Xbox One was known as Durango (which I still think was a cool name, but I digress). Recent comments from Ashan Rasheed give an indication as to the surprise developers had to Sony’s fairly last minute announcement.
He first said: “In early 2012, when the PS4 had 4GB of GDDR5, a developer in the EU region claimed: “Durango tosses the Orbis in every metric.”
He later added: “When 8 GB of GDDR5 was announced, certain developers were literally speechless.”
It would have been a very interesting dynamic if Sony had only managed to cram 4GB of RAM in to their Playstation 4. It would have meant that Microsoft would have enjoyed a clear advantage in terms of the amount of memory available to the games developers. Currently, the Xbox One and PS4 both use 8GB, but use DDR3 and GDDR5 memory, respectively. This means that the Xbox One requires careful management and use of the 32MB of on-die ESRAM to help make up for the lacking bandwidth of the DDR3 of the system (DDR3 operates at 68GB/s).
But if the PS4 had indeed only had 4GB, if you count the OS overheads, the Xbox One could have had anything from a 1.5 to a 3GB advantage in terms of memory. Clearly the PS4 would have still had a GPU advantage, 18 CU (Compute Units) vs the X1’s 12, meaning 1.84TFLOPS vs 1.32TFLOPS, but the lack of RAM could well have crippled the system.
It’s extremely likely that one of the major reasons developers were so surprised at Sony’s announcement is the extra costs associated with the 8GB of GDDR5 RAM. Prices regularly fluctuate on RAM, but the PS4’s RAM is currently around 30 dollars more expensive than the PS4’Xbox One’s. Cost and worries over yields of chips large enough to provide 8GB RAM are the reasons its thought Microsoft opted to go with DDR3 in the X1.
The memory systems inside both Sony’s and Microsoft’s machines is nothing short of complex. The PS4 uses HUMA (Heterogeneous Unified Memory Architecture) to allow ease of sharing data between the PS4’s CPU (the AMD Jaguar) and the GPU. Despite all of this, lack of memory could have easily led to lower resolution textures, longer loading time and a greater reliance on requiring more ‘loading screens’ between levels. Developers typically will try to hide these in level loading screens in short, unskippable cutscenes, or where your character very slowly walks perhaps while speaking with another. But less memory would mean these would be more frequent. Along with lower quality textures, lighting and possibly sound.
Asset streaming has become the normal since even the previous generation. The predecessor of the Playstation 4, the PS3 – much like the Xbox 360, had a distinct lack of RAM. The 512MB of total system memory (and that was before taking away overheads for the OS) simply wasn’t sufficient to load in all assets. Guerrilla games resorted to texture and audio streaming for Killzone 3, and a rather robust memory management system. Compared to today’s Killzone Shadow Fall, the developers clearly learned a lot, More on that here.
That’s not to say that there’s enough memory in even the PS4 and Xbox One. It’s likely the graphics artists will quickly run out of memory. The developers behind the middleware physics engine, Havok have said that there’s a lot of memory, but not so much that developers will be forever satisfied. More on that here.