IBM pares down Power7 blade server

Cuts cores and memory in half, but not price


One of the blade servers using IBM's new Power7 processors got lost in the shuffle last week. The single-socket Power Systems 701 and the dual-socket, double-wide Power Systems 702 were launched together, but there was another baby blade in a separate announcement, the Power Systems 700.

While the PS701 and PS702 blades have fully functioning eight-core Power7 chips running at 3 GHz, the PS700 has a half-dud chip that has only four working cores. IBM is sensibly riffling through the reject bins and making use of parts that would otherwise be tossed out.

This half-dud only has 16 MB of on-chip embedded DRAM L3 cache memory activated as well. This is segmented into 4 MB per core of L3 cache, like on the eight-core chips, with each core able to reach into the L3 caches of the other cores across the L3 memory controller. Each Power7 core on the PS700 blade server has 256 KB of L2 cache memory, just like on all other Power7-based machines, and the AltiVec SIMD and decimal floating point units are working on the chips used in the PS700, too. With the PS700 only having four cores, IBM has also trimmed back the number of DDR3 memory slots on the blade to eight; the PS701 has sixteen slots, and as El Reg explained last week, the PS702 is what happens when you slap two PS701s together to create a two-socket, double-wide blade that has 32 memory slots (256 GB max) and 16 cores.

With half the memory slots taken out, you'd think IBM would allow another 2.5-inch disk on the unit, or perhaps crank the clock speed up a little since it has the thermal room, but the company did not do that. The PS700 seems to be aimed at customers who want to keep the thermals down, such as telcos and service providers, or where having four cores and sixteen threads to throw at an AIX, Linux, or i application is sufficient oomph.

The PS700 may be half of a PS701, in that it has a rating of 45.13 on IBM's Relative Performance (rPerf) online transaction processing benchmark, compared to 81.24 for the PS701. But it does not cost half as much. The base PS700 blade costs $4,601 plus $100 a pop to activate each core; that blade includes 16 GB of memory, no disk, and no operating system for that $5,001. The 16 GB of memory costs $1,598, which means the blade and the activated cores account for $3,403 of that price, or $851 per core. By contrast, a base PS701, which comes with 32 memory, costs $5,503 plus $800 to activate all eight cores (which you have to do). The extra 16 GB of memory in the PS701 is worth $1,598 again, so once you back out the memory, the eight cores on the PS701 cost $3,107, or $388 a pop.

IBM is charging too much for the PS700, and customers should ask to pay $3,150 for a PS700 with 16 GB and all four cores turned on. This is the fair price given the work it can do relative to the PS701. ®

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