AMD's big bet on Llano CPU+GPU

Last week I was at ISSCC, an annual chip conference in San Francisco. Intel tends to dominate these conferences, not only because it is the largest semiconductor company in the world, but also because it is the only one shipping a 32nm microprocessor--and still the only one manufacturing chips using high-k material and metal gates in high-volume. (Earlier I previewed Intel's Westmere presentation at ISSCC.) While Intel may own the present, AMD believes the future belongs to Fusion. And at the conference AMD provided the first glimpse of some of the components that will go into its first Fusion APU, or Accelerated Processing Unit, slated to ship in 2011.

The idea of an APU is to combine an x86 processor with a capable graphics processing unit (GPU) on a single silicon die. AMD argues that simply adding more and more general-purpose x86 cores to a chip will yield diminishing returns since many--though certainly not all--tasks can be handled more efficiently by a highly-parallel processor with lots of little cores such as a GPU. AMD happens to have a capable DirectX 11 GPU, the ATI Radeon 5000 series.

This is not a new concept. It's the same idea behind GPU computing, but unlike Nvidia, AMD is in a position to physically combine the CPU and GPU. Intel already sells processors with a graphics controller--its Core i3 and Core i5 dual-core laptop and desktop chips--but it's not a single chip. Rather Intel combines a 32nm CPU with a 45nm GPU into one multi-chip package. Like AMD, Intel plans to put both on the same physical die, but the timing is unclear.

AMD first APU, code-named Llano, will also be the company's first processor manufactured at 32nm using high-k and metal gates. Llano will consist of four x86 cores, a DirectX 11 GPU and a DDR3 memory controller. It will be part of Sabine platform for desktop replacements and thin-and-light laptops. AMD will have a separate platform (Brazos) for ultraportables and netbooks with a new x86 design known Bobcat. This is also scheduled to ship in 2011, but AMD hasn't announced what process node will be used. Llano will also be used in mainstream desktops while another new core, Bulldozer, will show up in four- and eight-core processors for high-end desktops. Both will be 32nm processors and will be available in 2011.

Given all of the changes in Llano-a new process node and new materials on the first monolithic CPU and GPU--it's little wonder that AMD has largely stuck with the same design for the x86 as the current 45nm cores. AMD isn't ready to discuss the entire APU; instead it focused on these cores, each of which contains about 35 million transistors and occupies about 10 square millimeters (not counting the 1MB of L2 cache). Of course when you combine four of those with lots of cache, a GPU, memory controller and peripheral circuitry, the final APU will be much larger. AMD has previously said it will have around 1 billion total transistors at 32nm.

Most of the changes to the core have to do with better power management. For example, individual cores can be completely disconnected from the power supply when not in use to minimize power. The cores in Llano will operate at 3GHz or faster while using anywhere from 2.5 to 25 watts. AMD also talked about some of the changes in the circuit design required to make the design work with the high-k dielectric and metal gates. But the bigger questions surrounding the integration of the GPU remain a mystery for now.

From a user standpoint all that really matters is whether AMD can successfully deliver Llano on time. There's no doubt Llano represents a big technical challenge with a new process technology, new materials, and what looks like the first on-die GPU--all produced under a new manufacturing arrangement with the spin-off of GlobalFoundries. But the AMD has been talking about Fusion since it acquired ATI in 2006, and with Intel already shipping 32nm processors for the same mainstream laptops, AMD can't get there soon enough. If Llano arrives on-time, and it improves performance per watt and demonstrates the benefits of combining x86 cores with a powerful GPU, it should do a lot to make AMD more competitive.