IBM Revamps Cell-Based Linux Blade Server

Published: September 4, 2007

by Timothy Prickett Morgan

Having poured lots of money into the development of the "Cell" Power processor in conjunction with partners Sony and Toshiba, IBM has been trying to get some traction with the processor within its BladeCenter blade servers.

Last week, IBM did two things that might help the cause along. First, IBM rolled out a new blade based on the Cell chip, the QS21, which has twice the amount of main memory per processor. The original QS20 blade, launched last September, had two Cell chips running at 3.2 GHz, delivering 410 gigaflops of peak number-crunching performance. The QS20 blade had 512 MB of XDR memory per processor, which is not a lot of main memory, a 40 GB IDE disk drive, two Gigabit Ethernet ports, and space for a riser card that adds two Mellanox 4x InfiniBand host channel adapters. The new QS21 blade supports 1 GB of XDR main memory, which should help on memory-intensive workloads. (XDR is the fast memory technology created by Rambus that was supposed to make DDR2 main memory not necessary, remember?) Also on the memory front, the QS21 blade has room for two or four 512 MB I/O buffer memory chips for high-bandwidth links, which keeps the QS21 from choking on data as it comes in off the InfiniBand links. The other big change with the QS21 is that this blade only takes up one slot in the BladeCenter chassis rather than the two slots that the QS20 blade required. So even though IBM has not put faster Cell chips on the blade, customers can cram twice as many Cell blades in a rack now, doubling the compute density of supercomputers or special rendering applications that make use of these blades. That works out to 6.4 teraflops per BladeCenter chassis (which has room for 14 blades) and 25.8 teraflops per rack.

In addition to new technology, IBM also did one very important thing with the QS21 blades: slash prices. IBM was trying to charge $18,995 for a QS20 blade with two Cell processors, no memory, no extras. IBM's own Cell OEM partners making blades, such as Mercury Computer Systems, were charging half that. And so, with the QS21, IBM lowered the boom, and is now charging $9,995 for single-unit quantities of the QS21. The new QS21 blade will be available on October 26, and IBM's upgraded software development kit of the blade will be available the week before.

Just to be a wiseguy, and to try to get some business, Mercury has just announced a software development kit that rides on top of Terra Soft's Yellow Dog Linux that converts a Sony PlayStation 3 into a supercomputing node. This kit costs $399. Mercury is also selling a variant of the QS21 blade as well.

While the Linux 2.6.16 kernel has support for the Cell processor and its integrated eight AltiVec math units, IBM only supporting Fedora Core 5 on the QS20 blade; the QS21 blade gets real software and now supports Red Hat Enterprise Linux 5 Update 1.

What IBM has not done with the QS21, obviously, is upgrade the Cell processor itself that is on the blade servers. IBM was said to be moving to a 65 nanometer process with the Cell chip, and it seems likely that this new Cell-based blade is using a shrunken Cell clocking at the same speed but generating a lot less heat. There are unconfirmed rumors out there that IBM will use the 45-nanometer shrink to eventually put two Cell chips in a single package and then use future 32-nanometer shrinks to add more cores and math units to the Cell architecture. Other variants of the Cell chip with fewer math co-processors are also expected and will be used mostly for embedded devices and co-processor cards.

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