Sparc's future not about to be doused

With Sun Microsystems Inc.'s show of support for Linux on Intel, what is the future of the Sparc chip? Will it go the same way as Digital's popular but doomed Alpha processor?

No, says Sun's channel development manager of enterprise systems products Kelly Wilson, thanks to chip multithreading (CMT) technology. California-based Wilson says the next Sparc CPUs will run multiple software threads -- sets of instructions within an application -- simultaneously.

All current commercial CPUs have a single thread architecture which time-slices software threads -- thread one gets a chunk of time, then thread two gets a chunk of time and so on. Today's processors are fast enough to make this look simultaneous. However, says Wilson, processor speed has been doubling each year but memory access speeds have been doubling every six years, leading to a lag in memory. While putting more processors on a silicon wafer means you can process faster, it doesn't get rid of the DRAM latency – in fact, it is increasing.

Sun, says Wilson, has taken the tack of running multiple threads in each processing core.

Waikato University senior lecturer in computer science Murray Pearson says for software to take advantage of an EPIC-based CPU like Intel's Itanium it would have to be recompiled, whereas CMT processors will run any multithreaded software right now.

EPIC, or explicitly parallel instruction computing, is designed to overcome the fact that a processor is idle for 60 percent of the time when it's sequentially chomping through machine code by allowing simultaneous processing of chunks of suitably compiled programs.

Luckily, says Wilson, Unix OSes, databases and applications are already multithreaded and will be able to run on CMT chips without any change.

"You won't have to change the software to run on them. The programming model stays the same."

Pearson says while a lot of multithreaded CPU work has been done in the R&D labs, Sun would be the first to release such chips commercially. The first CMT chip, the UltraSparc IV, will come out next year with two threads and will have double the processing power of the current UltraSparc III, says Wilson, who attended a Sun conference for CIOs held in Taupo last month. Pin for pin they will be compatible so users can simply swap in the new processor.

But how does Sun get around the massive fabrication costs which eventually crippled the Alpha? Wilson says the cores to be used in forthcoming CMT processors are well defined, basic functional blocks which sophisticated CAD software can design almost automatically.

"This means a five-year design cycle for a single thread can be reduced to two years for multiple threads."

Sun is a "fab-less" design house, meaning it doesn't fabricate what it designs. It has partnered with CPU manufacturer Texas Instruments and piggybacks on its DSP (digital signal processing) manufacturing facilities.

"We don't have to spend US$2 billion on fabrication design. We take advantage of the fab technology they (Texas Instruments) use for DSP chips."

Wilson says by shrinking the design cycle Sun will lessen the risk of IT executives opting a certain architecture by being able to look ahead two years instead of five.

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