June 17, 2008
ClearSpeed Puts the Pedal to the Metal
UK-based ClearSpeed has launched its second-generation floating point accelerator lineup based on its new CSX700 “Callanish” ASIC. Like their GPGPU counterparts from NVIDIA and AMD, the ClearSpeed products are meant to be hooked up to CPU-based hosts to accelerate HPC applications that require large quantities of floating point operations. The new offerings include the e710 and e720 Advance boards and the CATS-700 1 teraflop server.
True to its focus on energy efficient HPC, ClearSpeed made power consumption the priority in the product refresh. In general, the three new offerings deliver slightly better raw performance than the previous generation, but much better performance per watt and double the memory capacity. With the products announced today, ClearSpeed is promising approximately 4 double precision (DP) gigaflops per watt. This is significantly higher than what the latest GPU, Cell or FPGA accelerators are able to offer.
The key to the new ClearSpeed products is the 90nm CSX700 processor, which replaces the 130nm CSX600. The CSX700 is a much more powerful chip than its predecessor, with twice the number of processing elements (196), two memory controllers, and an integrated PCIe x16 controller. The new processor deliver 96 DP gigaflops -- almost four times that of the CSX600 -- and sips just 12 watts under maximum load.
The more capable processor allowed the company to replace the dual-CSX600 configuration on the previous generation Advance boards with a single CSX700. ClearSpeed also saved a bit on overall power and cost by ditching the off-chip FPGA that acted as the PCI controller, a function that is now integrated on the chip. Each board has 2 GB of DDR2 memory -- again, twice as much as their predecessors. The result is that the new e710 and e720 Advance boards each achieve 96 DP gigaflops and draw just 25 watts of power. By comparison, the new NVIDIA 4-GPU S1070 board due out this August will achieve about 400 DP gigaflops at 700 watts, and AMD says its new FireStream 9250 will deliver over 200 DP gigaflops from 150 watts.
The e710 and e720 are functionally identical; they just have different form factors. The e710 is a low-profile, half-length PCIe board that slides into any standard PCIe-equipped server, while the e720 is a type 2 mezzanine card that fits inside an HP blade. The accelerator talks to the host at 2 GB/sec over PCIe x8. No extra power or cooling is required, which makes them easy to add to existing setups. No fans mean no moving parts, so there are no mechanical breakdowns to worry about. MRSP for the boards is $3,570, with an expected street price of under $3,000, in volume.
To take reliability to the next level, all memory, both on-board and on-chip, is error checked and corrected (ECC), which means protection from soft errors. The ECC support is a big deal, since the current GPU products for HPC offered by NVIDIA and AMD currently don't support this; application code that can't survive soft errors must go elsewhere to compute.
Since the new CATS-700 1U server makes use of the upgraded e710 boards, ClearSpeed has managed to deliver slightly more performance and almost double the energy efficiency compared the CAT-600 box that was demonstrated at SC07 in Reno. Using 12 of the new Advance boards, the CATS-700 provides 1.152 DP teraflops and 24 GB of memory. A single box uses just 400 watts, which is about the same as a typical low-power x86 1U server. A half-rack of 18 CATS-700 units hooked up to a half-rack of 18 quad-core x86 servers will yield over 22 peak teraflops -- more than enough raw performance to earn a spot on the TOP500 list.
ClearSpeed's main competitors are NVIDIA and AMD, both of whom have introduced 64-bit floating point support in their GPGPU product lines. With all three companies now in the double precision business, each is jockeying for position in a rapidly developing HPC accelerator market. ClearSpeed guessed correctly the latest generation GPUs would deliver only a fraction of their total single precision performance as double precision, which allowed the company to maintain a significant performance/watt advantage for DP math. And since neither GPU computing vendor offers ECC memory, only ClearSpeed can claim error correction and soft error protection.
"It looks like we're going to be in really good position with our 64-bit performance and price-performance and really out in front in terms of performance per watt." said Simon McIntosh-Smith, ClearSpeed's VP of Customer Applications.
ClearSpeed's strategy is to claim the HPC high ground against its GPU accelerator competition. The company says its emphasis on reliability and its focus on high performance computing gives its product the edge for HPC acceleration. With high double precision energy efficiency, system-wide protection from memory errors, and high MTBF, the company believes it offers a much more practical architecture than GPUs for highly scaled-out systems, especially as the petascale level is reached.
The IBM Roadrunner achieved a petaflop machine with Cell accelerators by mapping each Cell processor to an Opteron core, minimizing the CPU portion of the machine. But ClearSpeed estimates that just 50 racks of CATS-700/x86 servers will deliver a petaflop machine, and use only one fifth the power (750 KW) of the Roadrunner.
One downside for ClearSpeed is that the CSX700 ASIC, upon which its products are based, isn't a high-volume chip. Besides HPC, the company is looking to expand into the embedded systems market, where, for many applications, high FP performance is required. But commodity chipmaking is probably not in ClearSpeed's future. The CSX700 is fabbed by IBM, but at the 90nm process technology node, not the 65nm node IBM uses for the latest Cell chip or the 55nm node NVIDIA will build its new GPUs on.
As a small company with a niche market, it's more difficult for ClearSpeed to stimulate a software ecosystem around its architecture than it is for an IBM or an NVIDIA. Both the IBM Cell SDK and NVIDIA's CUDA development platform have a large base of potential users due to the use of the Cell for the PlayStation3 platform and the presence of GeForce and Quadro cards in PCs and workstations.
For its part, ClearSpeed is releasing version 3.1 (beta) of its CSX700 SDK, which includes its Cn compiler, a debugger, a profiler, and a fairly complete set of math libraries. According to the company, backward compatibility with the first-generation products is maintained.
But ClearSpeed's ability to provide the most energy efficient platform for HPC arithmetic is what sets it apart from the pack. The shift to petascale at the high end of the supercomputing market is going to demand low-power architectures. But even in the mid-range market, escalating oil prices and global climate concerns are causing everyone to rethink their HPC datacenter power budgets. At this point, the world's energy and climate problems might turn out to be ClearSpeed's best advantage.