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No cache usually means slower -- but not this time
IBM's new L3 cache-less design boosts server performance massively, says IBM
By Manek Dubash, Techworld | Techworld
Published: 01:00 GMT, 23 February 05
IBM's new server chipset, designed to support Intel's new four-way, 64-bit Xeon boosts four-way server performance by 38 per cent using real world benchmarks said IBM. And it uses an unusual technique to do so while, at the same time, said IBM, enabling the company to launch a product around it ahead of the competition -- mainly HP and Dell -- through the use of home-grown technology.
At the heart of the chipset is the Hurricane Node Controller, which provides merged processor-bus and memory-bus arbitration within a single chip. IBM said the high level of integration makes it faster and more reliable.
Product manager Jay Bretzmann said that the additional performance was achieved by effectively reversing a trend in processor and memory sub-system designs. For years, a key technique for boosting processor to memory interface speeds has been to insert a small amount of high-speed memory -- a cache -- between the two. IBM said it has eliminated expensive Level 3 cache memory, which on installed Xeons is up to 4MB and which Intel has just increased to 9MB.
Bretzmann said the Hurricane chipset instead uses a mainframe technique known as snoop bus filtering, which means processors in multi-way setups do not have to inspect each other's caches in the event of a cache miss but can instead go straight to main memory, cutting latency by one-third.
As a result, said Bretzmann, performance increases and, because of the lack of L3 cache, cost reduces by up to 40 per cent. He said the savings would be passed onto customers.
Other new features of the chipset include PCI-X 2.0 which enables 10GB Ethernet and support for up to 32 sockets, which allows greater scalability. Performance enhancements resulting from Intel’s own changes include a pair of front-side buses running at 667MHz compared to a single bus at 400MHz for a 3x CPU-bus bandwidth increase.
The first server incorporating IBM's Hurricane chipset will be the 3U X366, incorporating four 64-bit Xeons, four 2.5-inch SAS drives, and support for up to 64GB of memory carried on four DIMM cards. As well as a DVD drive and IBM's Lightpath diagnostics system, the X366 will optionally house a second, redundant 1300W PSU.
The new system will however, only include a maximum of 438GB of disk space, down from the 876GB of its predecessor, the X365. IBM said that this was the result of its shift from UltraSCSI to the new Serial Attached SCSI (SAS) interface, for which not many drive types were yet available. In addition, said brand manager Donn Bullock, most people used the internal drives on systems such as this for the OS, swap drives and log files, while main storage would be housed separately. As a result, internal storage was usually only around five to ten per cent full in real world usage, so less space was not a problem for most users.
Operating system support includes Red Hat and SuSE Linux, and all Windows Server editions, said IBM.
IBM said that it would make a further statement of direction in March, when there would be more information about systems supporting up to 32 CPUs). IBM said it had invested over US$100 million developing the chipset.
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