Bang For The Buck on Power7 Gen 2 Servers

October 31, 2011 Timothy Prickett Morgan

When the second generation Power7 servers were launched back on October 12, IBM said that it wanted to bring faster peripherals and doubled-up main memory to the Gen 2 machines, but it also wanted to keep the prices for the machines on the entry Power 710, 720, 730, and 740 machines the same as it was for the Gen 1 machines in terms of processor cards, processor core activations, and software. The new Power 770 and Power 780 Gen 2 machines also were supposed to be in the same pricing brackets.

As readers of The Four Hundred know, I like to do the math and figure out what the bang for the buck is for machines when they are launched. And thus, I took the time to update the monster, patent-pending Power Systems-IBM i motor bang for the buck table that takes a look at what it costs to buy the processor cards, activate cards, install IBM i, and pay for one year of Software Maintenance on each activated core in a machine. This table, which you can see here, includes the feeds and speeds of the Gen 1 machines as well as what I am calling the Power 750 Gen 1.5 box, which was announced in April along with double-stuffed PS7XX blade servers and which featured faster Power7 processors but not support for double-stuffed main memory or PCI-Express 2.0 peripherals. The Gen 2 machines are, of course, the boxes IBM announced back on October 12.

If you take a gander at the table, you will see that the pricing on the Power 710, 720, 730, and 740 entry machines is identical at least as far as processor cards, CPU cores, and IBM i licensing and support are concerned. So, as IBM suggested, the machines are indistinguishable in terms of raw performance and cost. But, as I reminded you when the announcements came out, the fact that the older machines cannot support 16 GB DDR3 memory sticks or PCI-Express peripherals–and do not include the extra PCI slot or the built-in RAID 10 disk controller–inherently means that the older machines should be worth less money. How much is subject to debate because it is not clear how many customers will need these features. But in a perfectly frictionless market, there’s no way they can have the same street price.

The Gen 2 Power 770 and 780 enterprise-class servers do not use the same processor features as their Gen 1 predecessors, and they do not cost the same in all cases either, so the bang for the buck for the two generations of machines cannot be the same. The Power 770 Gen 2 servers can have an eight-core Power7 chip running at 3.3 GHz or a six-core Power7 running at 3.72 GHz. The Power 770 Gen 1 machines had Power7 chips spinning at 3.1 GHz and 3.5 GHz. The good news, as you will see in the table, the pricing is exactly the same, so this is free extra performance. Depending on the configuration and the number of enclosures, the Power 770 Gen 2 machines offer between 4 percent and 10 percent more aggregate performance as gauged by IBM’s Commercial Performance Workload (CPW) online transaction processing test. Now, don’t get too excited, though. The cost of IBM i, at $53,000 per core, utterly dwarfs the cost of the processor cards and core activations. On a per core basis, the machines cost exactly the same because they have the same number of cores; on a per CPW basis, the Power 770 Gen 2 is anywhere from 4 percent to 9 percent cheaper.

On the Power 780 Gen 2 machines, when half of the cores are deactivated and run in Turbo Core mode at 4.14 GHz, the performance and price is exactly the same as the Power 780 Gen 1 machine and therefore the value for dollar is the same. Nothing to see here, move along. If you run them in standard mode, with all of the cores activated, the Gen 2 machine spins at 3.92 GHz compared to 3.86 GHz, which yields a tiny extra bit of performance but it is mostly negligible.

But hold on. There’s that funky Power 780 Gen 2 machine that IBM put out with two sockets per processor card (there’s only one per chassis in the machine, which has from one to four enclosures for a maximum of 96 cores). This machine uses six-core Power7 chips running at 3.44 GHz instead of eight-core processors running at 3.92 GHz, and IBM has scaled back the price on the processor cards and activations more or less in synch with the aggregate CPW. With the eight-core Power7 chips running at 3.92 GHz in the Gen 1 machine, performance ranges from 106,000 CPWs in a single-chassis Power 780 to 286,500 CPWs in a four-chassis configuration.

Switching to the Power 780 Gen 2 machine, there are twice as many sockets per enclosure, but a quarter fewer cores per socket so you only end up with 50 percent more cores per enclosure. That Power 780 Gen 2 machine ranges from 138,500 CPWs in one chassis with 24 cores and 550,700 CPWs for a four-enclosure with 96 cores. The processor card in the Gen 2 machine costs $55,773 and each core costs $5,422 to activate, compared to $57,429 for the card and $8,375 per core for the Gen 1 machine that has cores that spin at 14 percent higher clock speeds. On the Gen 2 box, the raw iron costs from $1.05 to $1.34 per CPW, compared to between $1.82 to $2.17 per CPW on the Gen 1 box using the 3.86 GHz processors and about the same on the Gen 2 box using the 3.92 GHz processors.

So in an ideal situation where the operating system didn’t cost so much, you might want to get this. Once you put IBM i on the cores, the faster cores come into play and lower core count come into play. The 96-core Gen 2 box costs $11.33 per CPW for the basic engines, software, and maintenance, while the 64-core Gen 1 box costs $13.24 per CPW. In general, the cost per CPW on the Gen 1 box is not that different from the Gen 2 box. Which begs the question: Why bother? I guess someone in the Power Systems base wanted more cores for less hardware cost, and I am guessing that it was an AIX shop somewhere.

This 96-core Power 780 Gen 2 machine is not available in a Turbo Core mode, and you might also note, IBM did not increase the Turbo Core speed, either, with the Power 780 Gen 2 machine, either. If anything would help IBM i customers, it would be faster clock speeds in Multi Core mode and even faster clocks in Turbo Core mode. But 4.14 GHz seems to be the Power7 speed limit.