Sony PlayStation 3 Review - Cell Broadband Engine Review

Of course the really important stuff is going on underneath that glossy black casing, and there’s no denying that there is some pretty serious hardware driving the PS3. The heart of the PlayStation 3 is the Cell Broadband Engine CPU running at 3.2GHz – this was co-developed by Sony, Toshiba and IBM. There are two main elements to the Cell chip, the Power Processing Element (PPE) and the Synergistic Processing Elements (SPEs). The PPE is based on IBM’s established PowerPC architecture and acts as the controller for the SPEs. The SPEs are independent RISC based processors that are used to spread the computational load, much like a multi-threaded environment in modern PCs. Each Cell chip contains eight SPEs, although only six of these are actually accessible. The seventh SPE is dedicated to specific operating system and security duties, while the eighth is locked out in an effort to improve production yield. With the PS3 designed to only need seven out of the eight SPEs, this allows Sony to still utilise chips with one failed core, thus vastly improving the yield. Of course this does imply that some PlayStation 3s will actually have eight functional SPEs, but with one working core locked out. Whether someone will figure out a way to unlock that eighth SPE remains to be seen, although if software is coded only to make use of six SPEs and not dynamically scale the idea of unlocking the eight core could be moot.

Despite being a single core unit, the Power Processing Element can execute two threads simultaneously in a similar fashion to Intel’s Hyper Threading technology that was seen in later Pentium 4 chips. Along with the six accessible SPEs, this allows the Cell chip to execute up to eight threads simultaneously, with the seventh SPE handling any OS overhead. There’s 256MB of XDR DRAM, which is an evolution of RDRAM – RDRAM made a brief appearance as the memory architecture of choice for the Intel Pentium III platform, but prohibitive cost saw it die out in favour of DDR memory. Rambus developed XDR specifically for high bandwidth environments like the PS3.

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