By Jason Stamper
Compaq Computer Corp says it isn’t worried by the IBM Corp- Sequent Computer Systems Inc merger earlier this week as the performance of its own version of NUMA technology, code-named PUMA (Practically Uniform Memory Access) leaves Sequent’s NUMA-Q standing.
IBM says a big reason for acquiring Sequent was to get its hands on the company’s NUMA technology, which it will use to boost up its entire range of servers. Compaq’s Wildfire servers, meanwhile, will be the first boxes to make use of its new PUMA architecture and are slated for shipment towards the end of the year. The Wildfires will outgun Sequent’s NUMA (Non Uniform Memory Access), Compaq claims, because it has managed to get latency down to a minimum. Latency refers to the performance hit caused by processors waiting for data to be transferred from memory – both memory local to the processor (cache), and remote memory accessed over the backplane.
Local memory latency will be as little as two nanoseconds for an eight-way system, according to Alphaserver product manager for the UK and Ireland Richard George. Adding further quad-processor building blocks will increase that latency to a maximum of ten nanoseconds, Compaq believes. Those figures compare to a local memory latency of around 180 nanoseconds for Sequent’s NUMA-Q systems. George says that 80% of the engineering effort on Wildfire was aimed at keeping latency to a minimum. Compaq says the secret behind its performance is that it backed away from a true NUMA architecture and went instead for a combination of linked nodes via a global hierarchical switch and NUMA-like memory addressing. The switched backplane gives a throughput of as much as 4.6Gbps, according to the company, whereas Sequent’s ‘IQ-Link’ SCI bus enables an aggregate 1Gbps link.
As already reported the Wildfires will use the new 767MHz EV67 21264 Alpha chip. Systems will be available initially in 16 or 32-way configurations but users will be able to add further quads. A 32 processor Wildfire should hit somewhere around 1.2 Gigaflops (1,200 million operations per second), while a 64 node cluster consisting of 512 processors is expected to hit 10 Teraflops (ten trillion operations per second), but that won’t be available before late next year. To put that in context, Digital’s current top of the range, the Alphaserver 8400 with up to 14 Alpha processors, achieves 200 Megaflops (two million operations per second). Operating systems will be a choice of Tru64 Unix, Windows NT or OpenVMS.
It’s not all good news for Compaq, however, as the Wildfires are behind their slated ship dates – they were supposed to have been available since April this year, but the company underestimated the engineering effort. For example, one of the components was expected to require 350,000 gates but really needed 500,000. Sequent’s take on latency, meanwhile, is that NUMA-Q latencies are halving each year, so it’s fast evaporating as an issue. There’s clearly no love lost between Sequent and Compaq since Sequent abandoned Compaq’s Tru64 Unix initiative to back IBM’s Monterey project.
