Socket Compatibility And The A85X FCH
Want Trinity? You Need A New Motherboard
Perhaps the biggest downer for early adopters of AMD’s Fusion initiative is the quickness with which the company is deprecating support for the Socket FM1 interface used to enable desktop-class Llano APUs. In much the same way that Intel replaced LGA 1156 with a very similarly-sized LGA 1155, AMD’s existing 905-pin socket is giving way to a 904-pin one.
Presumably, changes to the FM2 interface came about due to power delivery, since the PCIe and DDR3 I/Os shouldn’t be any different. Whatever the reason, though, Llano-based APUs won’t drop into FM2-equipped boards, and Trinity-based APUs won’t work in platforms with Socket FM1. As you can see in the image above, Socket FM2, on the left, and FM1, on the right, are keyed completely differently.
Meet The New A85X FCH
Although Trinity-based APUs are not socket-compatible with Llano, there’s nothing precluding motherboard vendors from attaching existing Fusion Controller Hubs to the new processor’s four-lane UMI interface. We actually have two FM2-equipped motherboards in the lab: ASRock’s FM2A75 Pro4 and a platform based on A85X, formerly referred to as Hudson-D4.
In reality, the two chipsets are pretty hard to tell apart. Basically, A85X gives you eight SATA 6Gb/s-capable ports, RAID 5 support, and the ability to divide the APU’s 16 lanes of PCI Express 2.0 into a pair of x8 links.
Otherwise, you’re looking at the same combination of USB 2.0 and 3.0 ports (4 + 10), the same four-lane Unified Media Interface, four lanes of second-gen PCIe, and four-channel audio (along with FIS-based switching, mSATA support, legacy PCI, and so on). AMD has not yet added PCI Express 3.0 support to any of its platforms, and isn’t expected to for some time.
More than likely, you’ll look to A75-based boards with Socket FM2 interfaces to save a little money, or A85-based platforms as a more feature-complete step up.
