IBM to snuff last Cell blade server

Six months until HPC shops go on Power, GPU diet


IBM has announced that supporters of IBM's "Cell" family of PowerXCell multicore processors have only another six months to buy more blade servers to build up their systems.

January 6, 2012 will be the last day that the BladeCenter QS22 blade servers, the last of three different Cell-based machines, will be available from Big Blue. After that, you will need to buy parts as you can find them from resellers or used-equipment dealers. That is also the last day that Cisco's InfiniBand expansion card for the QS22 blades will be available.

The QS22 came out in May 2008, packing two 3.2GHz PowerXCell 8i processors rated at 230 gigaflops doing single-precision calculations and 109 gigaflops at double precision. This QS22 blade had about five times the double-precision performance as the QS21 blade server it replaced, and included that InfiniBand mezzanine card from Cisco. It supported up to 32GB of DDR2 main memory and offered Gigabit Ethernet connectivity in addition to those InfiniBand links. With 8GB of memory, the QS22 blade server with two Cell chips cost $9,995 – not exactly cheap flops in today's day.

IBM withdrew the QS21 Cell blade, also a two-socket server, back in March 2010. This is the blade that Big Blue paired with its Opteron-based LS21 blade server to create the "Roadrunner" hybrid supercomputer at Los Alamos National Laboratory in New Mexico, the first machine to crest the petaflops performance level on a sustained basis as reckoned by the Linpack Fortran benchmark. When Roadrunner is decommissioned years hence, you'll probably be able to get QS21s on the cheap.

IBM originally had high hopes for the PowerXCell processors, which crammed a 64-bit Power core and up to eight synergistic processing element (SPE) coprocessors onto a single chip, which gave the Cell chips their number-crunching and graphics-processing power.

The plan back in early 2009 – before Nvidia had sucked all of the oxygen out of the coprocessor conversation with its Tesla family of GPU coprocessors and CUDA programming environment – was for IBM to launch a QSZ2 two-socket blade with lots more oomph. IBM never confirmed the exact specs of the QSZ2 machine, but when the fourth iteration of Cell chip was spiked by IBM for use in servers, the plan was to put two dual-core, 32-SPE Cell chips onto a single blade, yielding 1 teraflops of double-precision floating point performance, or about five times the current QS22 blades.

The QSZ2 blades were originally due in the first half of 2010 and would have been absolutely competitive with GPU coprocessors from AMD and Nvidia at double precision, and assuming IBM could have shrunk the Cell chips further and cranked the clocks this year, would have been keeping pace. Didn't happen.

IBM never explained why the Cell chips for blade servers were spiked, but hinted that in the future its commercial-grade Power chips would incorporate many of the functions of the Cell chips. This didn't happen with the Power7 chips launched last year, but it could happen with Power7+ or Power8 chips – or, more likely, not at all.

It seems far more likely that IBM will now focus on hybrid CPU-GPU combinations for certain HPC customers, and push the "Blue Waters" Power7 and BlueGene/Q PowerPC designs for those who want to push up into the 20 petaflops range.

Big Blue is still making Cell processors for use inside Sony PlayStation3 game consoles, and makes custom Power chips for use in game consoles from Microsoft and Nintendo as well. ®

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