Carrizo is supposed to be AMD’s next-gen APU. According to a leaked roadmap from December, the chip will replace Kaveri in 2015 and have GCN-derived integrated graphics combined with updated "Excavator" CPU cores. We don’t have new details on those elements of the chip, but Bright Side of News claims to have seen a "Preliminary BIOS and Kernel Developer’s Guide" for Carrizo, and that document reveals some interesting changes.
BSN says Carrizo’s memory controller will support both DDR3 and DDR4 memory. There’s no indication of supported DDR4 speeds, but the new memory type will presumably require new motherboards. However, Carrizo is supposed to be compatible with Kaveri’s FM2+ socket, so it may work in existing boards when paired with DDR3 RAM. Fingers crossed.
Somewhat surprisingly, BSN says Carrizo will integrate I/O connectivity: dual 6Gbps SATA ports, four USB 3.0 ports, eight USB 2.0 ports, and an SD interface. This platform functionality will be limited to BGA versions of the chip meant for notebooks, though. It will reportedly be disabled in socketed versions destined for desktops. The desktop-bound chips will rely on separate chipset silicon to provide I/O ports, just like Kaveri does today.
Another surprise is Carrizo’s PCI Express configuration, which is reportedly limited to 16 Gen3 lanes on the APU. Only eight of those lanes will be available for discrete graphics, BSN says, with the remainder split between peripheral connectivity and a four-lane link for separate chipset silicon.
None of this information is confirmed, of course, but it all sounds plausible if AMD is targeting Carrizo primarily at mobile systems. Most notebooks rely on integrated graphics and can get by with only a handful of PCIe lanes, SATA connectors, and USB ports. Integrating chipset functionality and cutting PCIe lanes also makes sense for small-form-factor and all-in-one rigs. The changes aren’t ideal for enthusiasts building powerful desktop systems, but perhaps AMD has something else in store for us. An FX refresh has to be coming eventually, right?