Interview: PS4 Developer Discusses Design Philosophy
Sony Computer Entertainment (SCE) Inc announced the overview of the "PlayStation 4 (PS4)," a next-generation stationary game console, in February 2013. We interviewed Mark Cerney, Lead System Architect on PlayStation 4, SCE, on the philosophy with which the machine was designed.
"The Single Chip Custom Processor," which SCE employed for the PS4, is equipped with eight "Jaguar" 64-bit CPUs, which are based on the x86 architecture and manufactured by Advanced Micro Devices (AMD) Inc, and the next-generation "Radeon" GPU, which has a performance of 1.84 TFLOPS. Why did SCE employ AMD's processor?
"We made that decision from the viewpoints of technology, time and business," Cerney said. "We started to design the PS4 in 2008. Since then, we had discussions with many companies on the adoption of any technology."
"The adoption of the x86 architecture made it much easier to develop game software because enough toolchains, numerical libraries and software that utilizes multimedia instructions are available for it," he said. "And compilers quickly supporting the latest extended instructions for vector operation are very advantageous."
Addressing issue of memory bandwidth
One of the elements that characterize the hardware configuration of the PS4 is its main memory. A bandwidth of 176 Gbytes per second was realized by using 16 4-Gbit GDDR5 memory chips, Cerney said.
The reason why SCE employed the GDDR5 interface instead of the DDR3 interface, which is commonly used for the main memories of personal computers, was to solve the problem of memory bandwidth, which had been the biggest bottleneck, he said.
"(Though it is a challenge in terms of cost and procurement,) we decided to offer a memory capacity of 8 Gbytes because of strong demand from developers," Cerney said. "We put priority on making a configuration that makes it easy for developers to create games so that many games will be made."
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Not making 'puzzle' for game developers
What was the basic concept for the design of the PS4?
"What formed the basis of the design was the thought that we should not make a puzzle for game soft developers," Cerney said. "For example, if we use eDRAM (on-chip DRAM) for the main memory in addition to the external memory, the memory bandwidth will be several terabytes per second. It will be a big advance in terms of performance."
"However, in that case, we will make developers solve a puzzle, 'To realize the fastest operation, what data should be stored in which of the memories, the low-capacity eDRAM or the high-capacity external memory?'" he said. "We wanted to avoid such a situation. We put the highest priority on allowing developers to spend their time creating values for their games."
Therefore, SCE decided to employ its own technologies required for game consoles while using the same basic architecture as used for personal computers.
"We received very positive responses to the concept of 'Supercharged PC Architecture' from developers because we made a drastic improvement to performance and made it easy to develop games at the same time," said Cerney, who developed many games. "It is hardware for which games can be developed really easily."
As for the "supercharged" parts, or the parts that SCE extended, he said, "There are many, but four of them are representative." They are (1) a structure that realizes high-speed data transmission between the CPU and GPU, (2) a structure that reduces the number of times that data is written back from the cache memory in the GPU, (3) a structure that enables to set priorities in multiple layers in regard to arithmetic and graphics processing and (4) a function to make the CPU take over the preprocessing to be conducted by the GPU.
"We are claiming that our company is leading innovations," Cerney said. "And we certainly employed our own distinguished technologies for the PS4."