Friday, February 22, 2008

The Future of CPU Integration

For years now, AMD has been crowing about the integrated DDR controller in its processors— something Intel’s chips don’t have. Integrating the memory controller with the CPU definitely has performance advantages, but what’s the next step in CPU integration?
For clues, consider Sun Microsystems’s new server processor, the UltraSPARC T2 (code-named Niagara 2). The first thing everyone notices about this “server on a chip” is that it has eight 64-bit processor cores—twice as many cores as the best server processors from AMD and Intel. In addition, each core can simultaneously run eight threads of execution—four times as many threads per core as the best Hyper-
Threading processor ever shipped by Intel. With eight processor cores per chip and eight threads per core, the UltraSPARC T2 can simultaneously execute 64 threads. Using Sun’s virtualization extensions, a single chip can run 64 different operating systems (or 64 instances of the same operating system) at the same time. Because each core runs at 1.4GHz, Sun likens the chip’s aggregate CPU performance to a singlethreaded chip running at 89.6GHz—a stretch of the truth, but impressive nonetheless. However, I consider the chip’s other integrated features even more impressive. The UltraSPARC
T2 has four integrated memory controllers, two 10-gigabit Ethernet controllers, an eight-lane PCI Express controller, and eight cryptography accelerators. Each dual-channel memory controller supports Fully Buffered (FB) DIMMs. The Ethernet controllers are multithreaded independently of the processors, so their actual throughput should handily beat an external Ethernet solution. The PCI Express interface runs at 2.5GHz, nearly twice as fast as the processor cores. The eight crypto engines support the most common security algorithms (such as DES and AES) and are much faster than general-purpose CPUs at this kind of number crunching. Sun isn’t exaggerating much by calling the
UltraSPARC T2 a server on a chip. And despite its unprecedented level of integration for a server processor, it consumes less than 100W and starts at less than $1,000. But the most interesting thing about the UltraSPARC T2 is what it foretells about x86 PC processors in terms of multicore integration, massive multithreading, and peripheral integration. Eventually, I believe, AMD and Intel will go with the flow of this Niagara.

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