IBM Rounds Out Big Unix Boxes with Power5+ Chips

Published: July 27, 2006

by Timothy Prickett Morgan

As expected, IBM this week got faster Power5+ processors into the largest members of its System p Unix server family, the p5 590 and p5 595 machines. The delivery of more powerful Power chips in these high-end machines fulfills a promise that Big Blue made to customers and to Wall Street that it would get Power5+ chips that had more oomph than the current Power5 chips into its big boxes during the third quarter.

IBM was also expected to further deploy its dual-core module (DCM) and quad-core module (QCM) variants of the Power5+ chips more fully across its entry server line, but apparently these machines will not be announced for a few weeks yet. It seems reasonable to assume that IBM is trying to get a clear message out about its biggest Unix boxes and how they compare to the just-announced dual-core "Montecito" Itanium processors from Intel and the servers that are built from that, which are expected to come to market in August and September from the likes of Hewlett-Packard, Fujitsu-Siemens, NEC, Unisys, Bull, and Silicon Graphics.

The basic design of the p5 servers has not changed with the introduction of the Power5+ processors into the machines, since the p5 machines were designed--as were prior generations of IBM Unix boxes and indeed, as are most servers these days--to accommodate multiple generations of processors. Basically, you put enough memory bandwidth, I/O bandwidth, and crossbar connectivity into the box so it can take faster processors when you get them to market a year or two later. A couple of years ago, everyone was aiming for much higher clock speeds on processors, and IBM was no exception in aiming high back then and was this week no exception in not hitting those clock speeds. According to vintage roadmaps, the Power5+ processors were slated to have 3 GHz or higher, but the chips used in the multichip modules (MCMs) inside the p5 590 and 595 servers, which span up to 16 or 32 sockets in a single system image, are only running at 2.1 GHz and 2.3 GHz. However, because the Power4 and Power5 generations of chips have two cores per socket, and the Power5 and Power5+ chips go further and have two threads per core, even with the diminished clock speed, these servers are still, on many workloads, offering the highest performance of any machine in the world.

It is probably more important to most of IBM's AIX customers that these machines be in the field because they offer headroom compared to the 1.65 GHz and 1.9 GHz Power5 MCMs also used inside the p5 590 and 595 servers. That said, some customers are always running out of room, no matter how big you build the boxes, and these companies tend to be the biggest spenders and the marquee accounts any vendor wants to keep happy. "We do have some clients that are pushing the limits on 64-core Power5 and Power5+ machines," explains Karl Freund, Karl Freund, vice president of product marketing for IBM's System p5 division within its Systems and Technology Group.

With IBM offering a quad-core package on Power5+ chips in its entry servers, you might be thinking, why not double up in the eight-chip, 16-core MCMs used in the p5 590 and 595 machines? For one thing, the QCM chips tend to be stepped down in terms clock speed, which is necessary to get two dual-core chips next to each other in the socket in such a way that they don't fry. Even if IBM could double the core count on its big boxes from 64 to 128 by doubling up cores in this manner, it might have to slow the clock speeds down by so much that the net gain would be negligible for the kinds of big workloads that the p5 590 and 595 are used for.

The p5 590 is, as was rumored a few weeks ago, getting a Power5+ MCM that runs at 2.1 GHz, up from the 1.65 GHz and 1.9 GHz Power5 MCMs. The more scalable p5 595 machine, which can have twice as many cores, is getting the 2.1 GHz Power5+ MCMs as well as a slightly faster 2.3 GHz version. Just as was the case with the Power5 chips, each core has a 1.9 MB L2 cache that is shared by the two cores. Each MCM has a 36 MB L3 cache per chip, yielding a total of 144 MB of L3 cache per MCM. Two MCMs are plugged onto what IBM calls a processor book (and what the industry calls a cell board), and each book can have 16 memory slots and up to 512 GB of 533 MHz DDR2 main memory. That means the p5 590 now scales up to 1 TB of main memory, and the p5 595 scales to 2 TB. A few months ago, IBM offered similar expanded memory on older p5 590 and 595 machines in the Power5 generation as an upgrade option, and new Power5 processor books that supported large page memory support. The latter can boost the performance of some database workloads by a few percent.

Freund says that IBM will post benchmark results on the TPC-C online transaction processing test that will show that the new p5 595 can deliver more than 4 million transactions per minute (TPM) at a cost of under $3 per TPM for a configured system (including maintenance and probably including a very large discount if history is any guide). IBM will be ramping up its benchmark labs to show off the big Power5+ boxes, as it usually does.

In terms of pricing, IBM is setting the prices for the new p5 590 and 595 machines using the 2.1 GHz and 2.3 GHz processors at approximately the same point as it was charging (until recent price cuts) for its earlier p5 590 and 595 machines using the 1.65 GHz and 1.9 GHz Power5 chips. A p5 590 with eight 2.1 GHz cores, 32 GB of memory, and two 36.4 GB 15K RPM disks costs $421,074. The way the pricing works out, that is a 4 percent premium over a machine using 1.65 GHz Power5 chips at current list prices, but the Power5+ machine will deliver about 27 percent more oomph. (These prices do not include operating systems or other features.)

A base p5 595 with 16 2.1 GHz cores, 64 GB of memory, and two disks costs $777,254, which oddly is less expensive than a machine using 1.65 GHz cores. A p5 595 using 64 of these 2.1 GHz cores, configured with 256 GB of memory and two disks, costs $2.67 million. If you want the slightly faster 2.3 GHz core, you are definitely going to pay for that extra 10 percent of processing power. A 16-core p5 595 using the 2.3 GHz cores, 64 GB of memory, and two disks costs $982,254. That's approximately 10 percent more processing power for a 26 percent premium. And on a 64-core machine, that 2.3 GHz option with 256 GB of memory and two disks costs $3.46 million, a 29 percent premium over a similar configuration using 2.1 GHz Power5+ chips.

The new p5 590 and 595 servers support IBM's AIX 5L V5.2 and V5.3 operating systems, as well as Novell's SUSE Linux Enterprise Server 9 and Red Hat's Enterprise Linux Server AS 4. Both machines will be available on August 11, with a few memory options coming in January 2007.

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