Rambus DRAM: Uncovering Facts & Burying Rumors

The lower pin count of RDRAM is quite attractive to companies outside of the desktop PC realm, including Sony, who just recently started shipping their highly anticipated Playstation 2 game console systems outfitted with 32MB of PC800 RDRAM. 

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Why did Sony choose RDRAM for the Playstation 2?  Did you think all the reasons we just mentioned in favor of RDRAM were just made-up facts?  ;)

The Playstation 2 needed quite a bit of memory bandwidth, without having to move to a larger memory size.  Using the same dual RDRAM channel architecture seen on Intel's 840 chipset, the Playstation 2 attains 3.2GB/s of memory bandwidth via two 16MB PC800 RDRAM devices operating on two independent 16-bit Rambus channels. 

With SDRAM, in order to gain the same bandwidth, you would have to make use of a minimum of 8 SDRAM devices (8 devices x 8-bits = 64-bit wide bus), which take up much more room and would result in a much larger memory size than Sony needed for the PS2. 

As you can see from the picture to the right, there are very few visible traces going from the Emotion Engine to the dual RDRAM banks and the two 16MB RDRAM chips occupy a total of 2.3 in^2 of space, and according to Rambus, the RDRAM solution reduces pin count by 30 – 65%, depending on whether you're using DDR or SDR SDRAM.