The company said it will charge customers $1.99 to download software that will enable 802.11n wireless functionality in the chipsets of most Intel Core 2 Duo- and Xeon-based iMac, Mac Pro, MacBook, and MacBook Pro computers.

Last week, when Apple announced its new AirPort Extreme wireless base station, it said the software would be included with the $179 device. "For those customers who wish to enable their 802.11n functionality but do not wish to buy a new Airport Extreme base station, we are making the software available for download from the Apple Online Store," says company spokesperson Teresa Brewer.

The $1.99 fee, she adds, is an accounting requirement. "When a significant feature enhancement is added, we are required to charge customers who previously purchased the product," Brewer says.

According to standard accounting practice, software vendors must either charge for significant enhancements to already-shipping products or recognize some of the initial revenue as deferred. In this case, Apple chose the former.

The enabling software will be posted to the Apple site for download when AirPort Extreme ships in early February. "Eventually the 802.11n software will be included with all new Macs that contain the appropriate hardware," says Brewer, who did not specify when the change would occur.

Earlier this week, a pair of Mac enthusiast Web sites reported that unnamed sources had pegged the download price at $4.99, more than twice the final fee.