UltraSPARC Patch Slows Performance

A glitch with Sun Microsystems Inc.'s Sun Blade 1000 workstations would impact few, if any, users. But the remedy will ultimately curb the performance of all those systems.

A glitch with Sun Microsystems Inc.s Sun Blade 1000 workstations would impact few, if any, users. But the remedy will ultimately curb the performance of all those systems.

The problem lies in the companys new UltraSPARC III chip. The errata has been linked to a new feature on the UltraSPARC III processor known as prefetching, an increasingly common implementation on chips that significantly improves system performance by speeding the retrieval of data.

But to swat the bug, Suns software patch disables the chips prefetching capability, effectively dampening the systems overall performance.

The problem was recently discovered during lab testing by Sun, an executive with the Palo Alto, Calif., company said. While company officials said the problem is "very rare and highly unlikely to occur," its potential threat to corrupt data was too great to ignore.

Unlike cases where processor errors are either flagged by the system or result in an easily recognizable problem, Sun said users will be unlikely to spot the data corruption, making the errata a more serious danger. The company has been contacting customers about the problem for three weeks, and a software patch has been up on its Web site for two weeks.

But while the problem—and solution—effectively dampens the systems overall performance, it also undermines the companys previously released system benchmarks.

How much of a hit users will see is difficult to gauge, Sun officials said, because it depends on what work they do. There is a possible performance degradation of 5 percent, which can move up or down depending on the work, they said.

Workstation users who do floating-point-intensive calculations will see the greatest impact, said Nathan Brookwood, principal analyst for Insight 64, in Saratoga, Calif.

"When you look at certain programs, such as structural stress analysis and some of the 3-D stuff, thats really predictable in terms of its behavior, and a prefetcher can do lots of good things," Brookwood said. "Or in this case, if the prefetcher is turned off, lots of good things dont happen."

While the software patch is considered a short-term solution, Sun confirmed it could be up to nine months before a redesigned UltraSPARC III chip will become available that will once again enable users to take advantage of the prefetching capability. If thats the case, Brookwood said, Sun should revise its benchmark scores.

Sun officials declined to reveal how many Sun Blade 1000 workstations the company has shipped since September or how many customers it was contacting.