Apple's Mac OS X market share has passed the 8 percent mark for the first time, a research company reported Wednesday.
In September, Apple's operating system ran on 8.2 percent of the computers that accessed the 40,000 sites monitored by Net Applications for clients, the company's data showed. The Mac's share of the OS market was up over August's by nearly four-tenths of a percentage point, the biggest one-month gain since May.
Apple tends to post significant increases in September, according to Net Applications. Last year, for example, Mac OS X climbed by 0.45 points that month.
Historically, Apple has run US back-to-school promotions into September to boost sales, especially to college students. This year's promotion, which ended September 15, offered rebates of up to US$299 toward the purchase of an iPod Touch or iPod Nano when bought at the same time as a Mac desktop or notebook.
In the last two years, Mac OS X's share has increased by 3 percentage points, a gain of 58 percent.
Microsoft's Windows, meanwhile, continued to slip in market share last month. Overall, Windows accounted for 90.3 percent of the operating systems powering the machines that accessed Net Applications' metric network, a drop of 0.4 percentage points from August, when the OS fell by nearly the same amount from July. That month was the last time that Windows maintained or grew its share.
Since the beginning of this year, Windows has lost 1.5 percentage points in market share.
Windows Vista's part of the OS pie grew again last month, primarily at the expense of Windows XP. In September, Vista accounted for 18.3 percent of all operating systems, an increase of nearly half a percentage point over August. Windows XP, meanwhile, fell by more than 0.8 points to 68.7 percent.
If Vista maintains its recent pace, it should break the 20 percent bar in late November or early December.
Other data collected by Net Applications showed that Apple's iPhone accounted for 0.3 percent of the devices connecting to the Internet in September, double the share of June, the month before Apple introduced the iPhone 3G and dropped the price of the handset to US$199.
Net Applications' operating system share and trend data is available online.