We were able to take a peek at AMD NDA information (aimed at engineers) that details the technical features of the Kaveri APU
. According to this information, Kaveri features a GDDR5 memory interface
consisting of four 32-bit memory channels. This is perfectly matching the width of a GDDR5 chip which is also 32-bit. However, the memory controller has to be set up in a way so that two 32-bit channels work in tandem, half-channel use is not supported. The total width is 128-bit, so the main advantage comes from higher clock speeds of GDDR5 memory. This is in addition to the 128-bit DDR3 interface that we already know from previous APUs. Usage of DDR3 and GDDR5 is mutually exclusive.