What processor does the MacBook Air use? Is it upgradable?

Officially, Apple only reveals that the MacBook Air has a 1.6 GHz or 1.8 GHz Intel Core 2 Duo processor (P7500 or P7700) and was "custom-built to fit within the compact dimensions of the MacBook Air". Apple also provides the following image to compare the size of the standard Intel Core 2 Duo processor to the one in the MacBook Air.

The always excellent AnandTech did some digging and discovered that the "packaging technology used for this CPU is what makes it unique; the CPU comes in a package that was originally reserved for mobile Penryn due out in the second half of 2008 with the Montevina SFF Centrino platform. Intel accelerated the introduction of the packaging technology specifically for Apple it seems."

After AnandTech published their initial speculation, Intel followed up with their own statement, noting that the MacBook Air "is using existing Core 2 Duo technology with a lower voltage spec in a new miniaturized packaging design."

Unsurprisingly, it is only a matter of time before Windows notebooks use this technology as well.

How do you upgrade the RAM in the MacBook Air? How much RAM of what type does it support?

The MacBook Air comes with 2 GB of 667 MHz DDR2 SDRAM onboard, and it cannot be upgraded. Those who need greater memory capacity should instead opt for a MacBook or MacBook Pro.

What are the capabilities of the external SuperDrive available for the MacBook Air? Can it be used with other Macs?

The external SuperDrive that is available for the MacBook Air for US$99 writes DVD+R DL and DVD-R DL at 4X, DVD-R and DVD+R at 8X, DVD-RW at 6X, and DVD+RW at 8X. It reads DVD at 8X, writes CD-R at 24X, writes CD-RW at 16X, and reads CD at 24X.

The external MacBook Air SuperDrive cannot be used with other Macs. Some have speculated that the USB 2.0 port in the MacBook Air has been "boosted" to provide extra power beyond that provided by other Macs. More recent speculation from AppleInsider concludes that the MacBook Air SuperDrive could work with other Macs if not for software restrictions and states that it is possible "Apple is offering the drive as a loss leader convenience for Air users, and doesn't want to support the drive on other systems because it's not making any money on it."

Regardless of which line of speculation you would prefer to believe, the external MacBook Air SuperDrive will not work with other Macs.