Windows XP is faster than the new Windows Vista Service Pack 1 (SP1) in completing common consumer and business tasks on PCs coming out of sleep mode, according to tests commissioned by Microsoft Corp.

The performance tests, conducted by Principled Technologies Inc. on Microsoft's behalf, showed that the older XP operating system remained faster than Vista SP1 in 61 per cent of the operations grouped in a consumer test suite, and faster than Vista SP1 in 46 per cent of the operations in the business-oriented head-to-head. The results were from time trials held on identical PCs after they'd come out of standby, a power-saving feature in Windows. Vista, like other operating systems, including Apple Inc.'s Mac OS X, calls the same mode "sleep."

However, when the same tests were run after a cold boot – with the PC's power turned on, the OS booted and the scripts run after two minutes – Vista SP1 came out on top in 74 per cent of the tested consumer functions, and 66 per cent of the business operations.

But no matter which operating system came out on top, the differences were small in virtually every case, said Principled Technologies. The total difference between XP and Vista SP1 in the 31 consumer tasks, for instance, was less than 5 seconds; of the 64 chores in the business scenario, 60 sported a difference of under half a second.

"Overall, Windows Vista SP1 and Windows XP performed comparably on most test operations," Principled Technologies concluded in its report.

The tests were run on four systems – two notebooks, two desktops – from Dell, Hewlett-Packard and Toshiba.

A fifth system, another HP desktop, was omitted from the aggregate results because it, "produced unacceptably high variability in its test results," according to Principled. Interestingly, that system showed XP was faster than Vista SP1 in more chores than any of the other test machines. In the consumer test set, for example, XP was faster than Vista SP1 in 74 per cent of the operations immediately after a reboot of the discarded HP.

Windows XP performed much poorer on the dropped HP in the business tests; it was faster than Vista SP1 only 31 per cent of the time, lower than the average of the other four PCs. But when it came out of standby, XP beat Vista SP1 in 53 per cent of the business-oriented jobs, a higher percentage than the other machines.

That, among other things, touched some nerves. Several users commenting on Microsoft's official Vista blog– where mention was made of the tests – took exception to Principled's conclusion that Vista SP1 and XP produced comparable results.

"Hard to believe when every other review site on the planet shows pretty much hands down [Vista] is slower on similar hardware," said a user identified as Ceinach. "I didn't even think this was a point of argument anymore. This statement is fairly stunning... It's like Microsoft is claiming the earth is still flat."

Computerworld's own tests, for instance, showed that file copying – a function Microsoft has said it spent considerable effort improving in SP1 – remained much slower on Vista than on Windows XP.

Principled Technologies also put Vista SP1 up against the pre-service pack version of the operating system. When armed with SP1, PCs finished 87% of the consumer chores faster than plain Vista, and wrapped up more of the business operations faster as well. But the speed improvements were meager, said Principled. Most of the business tests were completed just fractions of a second faster by Vista SP1 than by Vista.

"Overall, Windows Vista SP1 was more responsive than Windows Vista on most comparisons," the report stated. "Performance differences between the two operating systems were typically less than a quarter second."

Users noticed that, too. "All that work on Service Pack 1 and it's only a quarter second faster?" asked a user pegged as "eponymousnyc."

The two reports, one that outlines the consumer tests, the other for the business tests, can be downloaded in PDF format from Principled Technologies' site.