Kaveri Semiconductor Die and New Tech Process
Now that we’ve discussed the CPU and GPU components of the hybrid Kaveri processor, let’s take a look at it as a whole. The Kaveri, like its predecessors Trinity and Richland, is based on two dual-core Steamroller processing modules + an integrated GPU. In its maximum configuration, the new-generation hybrid processor only has four x86 cores, the more advanced integrated graphics core Radeon R7 being the single important difference from the previous models. The Radeon R7 features the new GCN 1.1 architecture and may incorporate up to 512 shader processors (a third more than in the maximum APU configurations of the previous generation).
Considering the small improvements in the Steamroller microarchitecture, the Kaveri is more graphics-oriented than its predecessors. The Richland’s x86 part accounted for 58% of the total transistor budget whereas the Kaveri’s x86 part accounts for 53%. The new APU is overall more complex, though. It is made out of 2.41 billion transistors as opposed to the Richland’s 1.3 billion. That’s even more than in Intel’s Haswell with GT3 graphics (1.8 billion). So the Kaveri series proves the fact that high complexity of a semiconductor die doesn’t necessarily translate into high performance. It does provoke serious manufacturing problems, however.
The Kaveri is manufactured on 28nm tech process by GlobalFoundries. Optimized for high transistor density, the process is referred to as SHP or Super High Performance. The SOI technology is not used. As a result, the Kaveri semiconductor die is 245 sq.mm large, which is about the same size as the 32nm Richland die.
The downside of the high transistor density is low frequency potential. The top clock rate of the Kaveri’s x86 part is 3.7 GHz whereas its integrated graphics core is clocked at up to 720 MHz. Manufactured on 32nm tech process with SOI, the Richland’s CPU and GPU were clocked at up to 4.1 GHz and 844 MHz, respectively, which is about 10-15% higher. As a kind of compensation, AMD promises some power dissipation reduction in the new APUs whose desktop modifications have a specified TDP of 95/65/45 watts. The Richland series had a peak TDP of 100/65/45 watts but the 45W models were not widely available. Energy-efficient Kaveri products with a TDP of less than 95 watts are not available yet, either.
Thus, the Kaveri model range for desktop PCs consists of only two products: A10-7850K and A10-7700K. They have four x86 cores each but differ in clock rates. The A10-7850K has a base clock rate of 3.7 GHz whereas the A10-7700K, 3.4 GHz. The Turbo Cache technology can boost the clock rate to 4.0 and 3.8 GHz, respectively. The APUs differ in the number of shader processors. The A10-7850K has the maximum of 512 shader processors while the A10-7700K has 384, just like the Richland. The integrated graphics core is clocked at 720 MHz in both Kaveri models.
Socket FM2+ Platform
The Kaveri processors come out together with the Socket FM2+ platform which introduces a new CPU socket. It was meant to add DDR4 SDRAM support in the first place but something went wrong and the Kaveri’s memory controller only supports two standard DDR3 SDRAM channels. Later on, AMD gave up the idea to support DDR4 in the next APU generation, codenamed Carrizo, which was to be compatible with Socket FM2+. So it turns out now that the new socket has only been introduced to make users upgrade their mainboards.
As expected, Socket FM2+ is very similar to Socket FM2 but has differently positioned keys which make it impossible to insert a new Kaveri processor into an old Socket FM2 mainboard. Socket FM2+ mainboards, on the contrary, are compatible with older processors of the Trinity and Richland generations. Old processor coolers can be used with Socket FM2+ mainboards, too.
Socket FM2+ mainboards have been around for quite a while already, so you should have no problems finding one for your Kaveri APU. They are based on the Bolton series chipsets (A88X and A78) which have almost the same specs as their Hudson predecessors (A85X and A75).
The new functions offered by Socket FM2+ mainboards are limited to their support for PCI Express x16 3.0 and high-speed DDR3 SDRAM (up to DDR3-2400). But both features are actually provided by Kaveri APUs which have updated PCIe and memory controllers. So if you install an older APU on your Socket FM2+ mainboard, you won’t get the PCIe x16 3.0 and DDR3-2400 SDRAM support.
The A88X and A78 chipsets only have one new capability of their own. It is the upgraded SATA RAID controller which adds TRIM support for RAID0 arrays built out of solid state drives.