IBM Boosts Power4+ Chips for pSeries 655 Midrange Line

by Timothy Prickett Morgan

IBM this week kicked up the speed on the Power4+ processors that are used in its midrange pSeries 655 servers. The speed bump on certain pSeries configurations is the amounts to about 19 percent on integer and floating point workloads, which is good for customers--particularly in the high performance computing market where flops are important. Perhaps most significantly, IBM is offering the 1.7 GHz Power4+ prices at the same price as the 1.5 GHz version it put into the pSeries 655 in May 2003.

The pSeries 655 is an eight-way capable machine that has a single multichip module (MCM) with four dual-core Power4+ engines. Customers can activate half the cores on each chip to make what looks like a four-way SMP server to AIX, IBM's Unix variant, or activate all the cores to make an eight-way box. Either way, each pair of Power4 cores on a single chip inside the MCM has a shared L2 cache that is 1.5 MB in size. For workloads that are more L2 cache sensitive, only activating four Power cores per server is a better option since each core gets its own 1.5 MB cache to play with.

The pSeries 655 was announced in November 2002 with 1.2 GHz and 1.45 GHz Power4+ processors. In May 2003, the pSeries 655 was available in two configurations: a four-way using 1.7 GHz Power4+ chips or an eight-way using 1.5 GHz Power4+ processors. IBM might have been having yield and heat issues with the 1.7 GHz chips last year, which would explain why it was only offering them in four-ways. This would give customers with cache-sensitive workloads 20 percent more performance than they would get with a 1.5 GHz chip. And the commercial customers who would want an eight-way box would care more about aggregate performance than L2 cache amounts, so dropping the speed of the eight-way pSeries 655 to 1.5 GHz was probably not that big of a deal. It would also run cooler than an eight-way 1.7 GHz model.

With this week's announcement, IBM is offering an eight-way pSeries 655 with 1.7 GHz Power4+ processors, 4 GB of main memory, and two 36 GB disks for the same $70,000 it was charging up until now for an eight-way using the 1.5 GHz Power4+. The price of the 1.5 GHz eight-way machine, says Jim McGaughan, director of pSeries marketing at IBM, has been cut to $61,910. There is no four-way configuration using the slower 1.5 GHz Power4+ processors, but there is a four-way pSeries 655 with 1.7 GHz processors with 4 GB and two disks that now sells for $47,625.

In addition to the processor changes, IBM has also expanded the maximum main memory capacity of the pSeries 655 from 32 GB to 64 GB.

All of these machines include an AIX 5L 5.2 license. The 1.7 GHz Power4+ processors will be available worldwide starting February 6.

The pSeries 655 servers can be clustered together using the "Colony" SP2 switch or the faster "Federation" HPS switch when running AIX. Customers running Linux workloads and IBM's Cluster Service Manager software have to get by with Gigabit Ethernet as interconnection fabric until Big Blue has it tweaked to support the Federation switch. McGaughan says that Federation support on the pSeries 655 running Linux will happen this year, and the word on the street is that it will happen around mid-2004. That is, by the way, just after when IBM is expected to debut its Power5-based "Squadron" servers, which are rumored to be coming in April or May in eight-way configurations.

The high-end 32-way pSeries 690 is the only other machine that has the 1.7 GHz Power4+ chips yet. The 16-way pSeries 670 is still using 1.5 GHz processors. The question many IBM customers want to have an answer to is when Big Blue is going to get around to shipping an even faster Power4+ chip, perhaps hitting 2 GHz or higher. There has been plenty of speculation and rumor about such a thing, and IBM wants to keep pace with the benchmarks that rival Hewlett-Packard has been showing with its 64-way 1.5 GHz "Madison" Itanium 2-based Integrity line of servers, which are also known as Superdomes. In November 2003, HP broke through the 1 million transaction per minute (TPM) barrier on the TPC-C online transaction processing benchmark using a 64-way Superdome running HP-UX 11i and Oracle 10g Enterprise Edition. Specifically, this machine processed 1,008,145 TPM at a cost of $8.33 per TPM after a staggering 48 percent discount on hardware, software, and maintenance over a three year term.

IBM has fallen behind Superdome in terms of aggregate performance, but still benefits because in a CPU-based pricing world for software, a Power4 core still does almost twice as much work (at least as far as TPC-C is concerned) as a Madison chip in the Superdome.

In June 2003, a 32-way "Regatta-H" pSeries 690 tested at 763,898 TPM running IBM's AIX variant of Unix and its own DB2 database. After a 41 percent large systems discount, the cost of this machine came in at $8.31 per TPM. In September 2003, IBM ran the TPC-C test on the same 32-way pSeries 690, only this time running Oracle 10g on AIX. That machine could do 768,839 TPM at a cost of $8.55 per TPM, again after a hefty discount. The speculation was that a 2 GHz Power4+ MCM for the pSeries 690 might have come out before the end of 2003, but that clearly didn't happen. But IBM sources have said that the Power4+ still has some gas in it. If IBM can get to 2 GHz, that should bring an extra 15 percent to 20 percent more performance on the TPC-C test, or around 900,000 TPM. If IBM boosts main memory on the machines to 1 TB, as HP did with the Superdomes, it could push performance on the TPC-C benchmark well above 1 million TPM. If IBM can get to 2.1 GHz or higher, tune Oracle 10g a bit more, it could even go a bit higher than 1 million TPM and it might even be able to get the bang for the buck down to $7.50 per TPM or so.