MacBook Air Comes with a Special USB Port for SuperDrive

Very few of us actually have to deal with external USB DVD burners since even the slimmest laptops sold in America have an optical drive. Exceptions are UMPCs, imported tiny Japanese sub-notebooks, and now Apple MacBook Air. Owners of the former two devices are already accustomed to compromises. On the other hand, Mac folks have been bashing Apple about the Air omission of a built-in DVD writer and limiting them to one and only optical drive option that won't even work on other Macs, let alone PCs.

It looks like Apple has a good technical reason. In order for a USB burner to operate completely bus-powered, Apple had to ask Intel to design a motherboard whose USB port exceeds normal parameters to supply more power (> 500mA). Then Apple had to come up with a special SuperDrive that can tolerate the electrical load from this high-powered port. The $99 slot-loading optical drive therefore can't work with other machines because of the power requirement.