Docs show four DRAM controllers, although only two are in use by default

Jan 17, 2014 07:04 GMT  ·  By

Despite how good the graphics have become in AMD's Accelerated Processing Units, none of them ever use GDDR5 memory, mostly because they need to use the system memory, which is always DDR3. This might finally change though, at some point in the future.

For this hope, we have some very specific AMD documents to thank, documents that describe the specs of the Kaveri APUs in more detail.

This is the part where we would love to be able to say that Advanced Micro Devices has enabled GDDR5 support on its APUs, or that the A-Series chips at least have the option of enabling it in the BIOS.

That's not the case though. If there was GDDR5 support, the info would have surfaced before. Certainly AMD would not have willingly kept quiet about it in its recent (and extensive) product briefings.

Still, there is enough information to assume that AMD fully intends to eventually release an APU with GDDR5 support.

Which, in turn, would mean that AMD's OEMs would make motherboards with GDDR5 integrated chips, or maybe it would be integrated into the APU itself somehow, like Intel's Haswell CPUs have 128MB of on-package eDRAM.

Whichever the case, it won't happen this year, or the next, which some might call a crying shame.

Anyway, Beyond3D forum member "yuri" is the one responsible for all these speculations, as it was that person that combed through AMD's latest BIOS and Kernel Developer's Guide (BKDG 3.00).

There, a reference was found to a Gddr5Mode option for each DRAM controller. Speaking of which, there was a second interesting reference: there are four DRAM memory controllers (DCT0-3), quad-channel memory as it were, though only two are actually in use (DCT0 and DCT3).

Since memory bandwidth is a major factor in the scaling of a processor's graphics performance, we suppose it makes sense that AMD would be preparing for one or both of these features. Maybe it was going to include it in Kaveri, but figured that hUMA would be enough for now, so it kept these assets as trump cards for a later date.