AMD Kaveri Support Document References Quad-Channel Memory & GDDR5

Posted on January 17, 2014 10:00 AM by Rob Williams

Well, this is rather intriguing. According to details found (original source) in a Kaveri-related support document, it looks as though AMD had mulled the idea of shipping its latest APU with a couple of major features. At the forefront, the document references four memory channels, bearing the names DCT0 ~ DCT3. Of these, just 0 and 3 are operational. The reference goes on to state, “Software must not attempt to configure ‘DCT1′ or ‘DCT2′”.

That can mean just one thing: The original design had quad-channel in mind, but at some point AMD decided to stick to the traditional dual-channel design we’ve come to expect of mainstream PCs. At the current time, users would need to go with Intel’s high-end X79 platform to take advantage of quad-channel DRAM configurations, so to see something like this referenced on a mainstream part (rather than AMD’s FX line) is pretty surprising.

AMD Kaveri Support Document - GDDR5 and Quad-channel

The same support document refers to “Gddr5Mode”, but states that it might not be supported by the given processor – and it isn’t. In the image seen above, it clearly states that “GDDR5 memory is not supported”, making this an even more interesting finding.

GDDR5 isn’t a drop-in replacement for DDR3 as our current software wouldn’t be able to take advantage of it (or our EFIs, for that matter). The mention is still interesting, though, but not too surprising given Sony’s PlayStation 4 makes use of an AMD APU and happens to take advantage of GDDR5. The reason that was possible, of course, was because Sony designed the operating system around GDDR5 – something I’m willing to bet had more to do with security than performance.

Despite neither of these features being available on the desktop-equivalent of Kaveri, it does lead us to believe that AMD might be considering a quad-channel design for the next-generation. That might be a bit overkill for a mainstream processor, but when both the CPU and GPU make use of the same DRAM, it could actually be the first realistic use of a quad-channel controller for regular desktop users.

  • Jamie Fletcher

    Different model revisions, the pin outs may stay the same, but internally different. Makes sense. The extra channels would really help with the GPU aspect of the APU, same for GDDR5 (high bandwidth, rather than low latency), but I think it’s a case of the two being linked together, as is the norm with GPU designs. Four times 64-bit controllers, 256-bit addressable memory over GDDR5 – sound familiar?

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