Microsoft has claimed that users will be able to complete a Windows 8 upgrade much faster, in some cases in one-tenth the time it took similar-configured PCs to upgrade to Windows 7.
The time savings quickly accumulate the more files are on the to-be-upgraded PC, said Christa St. Pierre, a member of Microsoft's Setup and Deployment team, in a long entry on the company's "Building Windows 8" blog.
According to St. Pierre, a clean install -- where all files and data are wiped from the drive prior to installing Windows 8 -- should wrap up in 21 minutes, 35% less time than the 32 minutes Microsoft said it takes Windows 7 to do the same.
For what Microsoft called a "medium upgrade," one on a PC with 213,000 files and 77 applications, Windows 8 is three times faster, finishing the upgrade in just 42 minutes, versus Windows 7's two hours and 11 minutes.
The real savings show when machines sporting between 430,000 and 1.4 million files with between 90 and 120 applications are upgraded: In those scenarios, Microsoft promised that Windows 8 was between four and ten times faster in the time trials.
St. Pierre acknowledged that Windows 7 was no greyhound.
"If you had a large number of files on your system, you may have seen that installation times in Windows 7 didn't scale very well," she said, citing a graph that showed a "super upgrade" on a PC harboring 1.4 million files and 120 applications taking eight and a half hours.
That kind of time was actually on shorter end of Windows 7's upgrade duration: Two years ago, a different member of Microsoft's deployment team warned that some upgrades from Vista to Windows 7 could take up to 20 hours .
St. Pierre also said that only Windows 7 to Windows 8 upgrades will transfer applications, meaning that anyone migrating from Windows XP or Vista will be offered a clean install that transfers only personal files, or in the case of Vista, personal files and the user's Windows settings.
She did not specify which versions of the decade-old Windows XP could be upgraded to Windows 8, but said that in some cases, depending on the PC's hardware, it would be possible.
"We expect that many systems running Windows Vista and even Windows XP will also be eligible [for Windows 8 upgrades]," St. Pierre said.
St. Pierre added that upgrade from XP to Windows 8 will let users of the former transfer "personal files" -- she did not define that term, however -- perhaps making the migration more generous than Windows 7's.
That 2009 operating system only provided a clean install that required users to move files off the PC to an external hard disk drive using Windows Easy Transfer.
For Windows 8, Microsoft has ditched the transfer utility and included the personal file-retention feature in the overall upgrade process. However, St. Pierre did not spell out whether the Windows 8 setup will copy those files to external media -- perhaps a USB thumb drive -- or whether they would somehow be stored on the PC's primary hard disk drive before being restored after the upgrade completed.