"With POWER7  you get twice the performance, use half the power and four times the virtual capacity for the same price as POWER6".  IBM 08 Feb 2010.

Now IBM have officially announced the POWER7 range I thought I'd test some of IBM's bold claims for performance vs purchase price, power consumption and space savings for the new POWER7 range by comparing it with the POWER6 range. Have they really changed that much? The move from POWER5 to POWER6 was a great improvement in performance and brought with it some great new features, but the price was still very high and left open the door to a price contest with x86 alternatives and some challenging TCO comparisons. I thought I'd start by taking a look at the really popular entry point in the POWER range - the 550 (4U rack mount) . First thing to note is that it is now called the 750 (finally the numbers make sense!) So how does it compare on price/performance with the POWER6?

I'm using the IBM POWER relative performance metric rPerf to create comparable systems. The actual performance you get from these systems will depend on how well your software/middleware makes use of parallel processes to drive the four threads per core capability of POWER7, but the rPerf is a great place to start.

Lets look at the lower entry point to begin. The smallest 750 has six 3.3Ghz cores in a single socket giving an rPerf figure of 70. For the equivalent POWER6 system the nearest is eight 4.2Ghz cores in 4 sockets giving your an rPerf of 68.

In both the entry and high-end examples I have tried to create a realistic set of resources so that we have a fair comparison. I have chosen the following specification for both a POWER6 and POWER 7 system

  32GB RAM

  2 internal disks

  2 SAS interfaces

  on board Ethernet +2 port PCI card

  2 x 2 port 4GB Fibre

  No PowerVM

  3 yr SWMA

In this example the POWER6 list price adds up to £124,650, the POWER7 price list price is £50,917. 

It's worth noting that the 750 has 3 more CPU sockets to expand into, and greater headroom for memory. 

So how does a fully expanded 750 compare with POWER6 systems?

The biggest fastest POWER7 750 is the 32 core 3.55Ghz 4 socket machine with an earth shattering rPerf of 331. To get this compute power form a POWER6 machine you have to leapfrog up the range to the p595 with 35 5.0Ghz cores giving you an rPerf of 335. You can probably guess which is going to be cheaper, but lets work through the example for fun. (I don't get out much these days anyway)

Again trying to make a real world example I have added the following specification to both examples.

  512GB RAM

  1 I/O Drawer

  8 73GB disks

  Four SAS interfaces

  4 x 4 port PCIe 1Gb Ethernet

  4 x 2 port PCIe 8Gb FC

  PowerVM Standard

  3yr SWMA

For my example configs the POWER6 p595 list price is £2,846,828 and the POWER7 750 list price is £427,661. Obviously there are some advantages with a p595 and in some circumstances the p595 architecture may produce better performance, but with such a dramatic reduction in purchase cost coupled with reduced data centre space and low power consumption (1950W for the 750, something like 6000W+ for the 595) it has to be worth a look.