A group of researchers has described Microsoft's upcoming Windows Vista Service Pack 1 as a "performance dud".

Researchers from the EXO Performance Network claimed that a series of in-house benchmark tests showed that users hoping to receive a speed boost from the update will be disappointed.

"After extensive testing of Release To Manufacture and SP1-patched versions of Vista it seems clear that the hoped-for performance fixes that Microsoft has been hinting at have not materialised," the group said in a company blog.

The tests were run using tools from Devil Mountain Software, which also hosts the group's site. The researchers used a Dell notebook with 1GB of Ram for the tests.

The benchmark tests measured performance in Microsoft Office 2007, multitasking and streaming media.

The results from the SP1-patched system were nearly identical to those from the version of Vista released to manufacturers, according to the researchers.

"The thinking goes that SP1 will address all of these early performance issues and somehow bring Vista on par with, or at least closer to, XP in terms of runtime performance," said the report. "Unfortunately, this is simply not the case."

The researchers concluded that users waiting for the update to fix pokey performance will not get any respite in the short term.

"If you have been disappointed with the performance of Windows Vista to date, get used to it," they wrote. "SP1 is simply not the panacea that many predi cted."