Please show me these 12v and 1000mA USB specs - I have the USB 2.0 and USB 3.0 specs open, and 2.0 says that USB High-power is 5 unit loads (500mA) at 5v. USB 3.0 sets high-power to 900mA at 5v. (Specs here:
http://www.usb.org/developers/docs/) USB 3.0 has a special "powered B" connector spec that does 1000mA, but that's also at 5v.
Is it possible that Apple is using a non-standards compliant USB port, and it's drivers will allow a device to request more than 5 unit loads? The Win7 driver might limit things to 5 loads.
The MBA port is known to be non-standard and able to supply more than 500mA.
"the sole USB port has been boosted past its specifications to supply enough power to use the drive with just the data cable rather than a direct power connection"
http://www.electronista.com/articles/08/01/23/macbook.air.usb.details/