IBM releases 256-core UNIX beast

If you thought your quad-core CPU was a modern day technical marvel, then you've got some catching up to do in the world of high-end servers.

IBM has just unveiled its 256-core monolithic Power 795 UNIX server, which can accommodate up to 8TB of memory.

Measuring 201.4cm (42 rack units) tall, the Power 795 is based on IBM's new Power7 architecture, and is divided into a parallel configuration of 'books', each of which contain four CPUs and 32 DDR3 DIMM slots. The CPUs themselves come in both eight-core or six-core flavours, and feature 256KB of on-die Level 2 cache per core, plus 32MB of Level 3 cache. What's more, IBM says each core can handle up to four hardware threads.

A Power 795 unit can provide a home for eight of these books, meaning it can scale from 24 cores to a mammoth total of 256 cores. Interestingly, it also looks as though IBM has been keeping an eye on Intel's automatic overclocking TurboBoost technology, as it's introduced a similar-looking TurboCore mode for the processors in this server.

Two performance modes are available to the server: MaxCore (standard) and TurboCore, where the latter pushes up the clock speed and also provides access to additional Level 3 cache. According to IBM, an eight-core CPU in the server goes from 4GHz to 4.25GHz when it's in TurboCore mode, while also doubling the amount of Level 3 cache available to each core.

However, the server is limited to using 128 cores, rather than the full 256, if you want to use the TurboCore mode. It's also worth noting that the TurboCore mode isn't applicable to 24-core books based on six-core CPUs, which operate at a set frequency of 3.72GHz.

The big questions, of course, are how fast it is and how much power it drains, and IBM reckons it's on to a winner here. For a start, IBM says the new hardware quadruples the throughput of its previous flagship server, the Power 595 (based on the Power6 processor architecture), while sitting in the "same energy envelope" (consuming a similar amount of power).

IBM is also boasting about the server's performance compared with its competitors. The company's chief technical strategist of performance marketing, Elisabeth Stahl, points to some benchmarks on her developer blog. Running the TPC-C benchmark, Stahl says a 192-core Power 780 cluster based on the same Power 7 architecture was 2.7 times quicker in terms of performance per core than Oracle's equivalent biggest server, when using IBM's DB2 database. "Oh, and by the way, it was 40 per cent less expensive," notes Stahl.

In the test, the Power 780 cluster clocked up 10,366,254 transactions per minute, beating the score of 7,646,486 from Oracle's SPARC T5440 by around 35 per cent. IBM also proudly boasts that the score trounces the 4,092,799 from HP's Integrity Superdome-Itanium server by over 153 per cent. "HP's best result is over twice as expensive as the IBM result," says the company.

IBM says the new Power 7 servers have a starting price of $6,500 US (£4,153), but advises customers to call for a customised quote.