The second most contentious design decision regarding Air relates to the elimination of the internal SuperDrive.
Now, this isn't new in the world of small computers. Many systems in the ultra-portable class have offloaded the CD/DVD drive to an external enclosure, or to a docking station.
So they have an excuse. But what matters here is not that they did so, but how they did so.
And managed to get almost everything wrong in the process.
The problem, you see, lies in their decision that the external SuperDrive be a "bus-powered" device. One that's powered by the Air's USB port, and one that doesn't need an external power adaptor.
But SuperDrives are power-hungry creatures. Especially when they're burning a DVD at speed. In fact, that particular process consumes more power than is available via a single standard USB port.
Other manufacturers have solved the issue in a couple of ways:
1) Require an external power brick.
2) Run the drive at half or quarter speed.
3) Use a special USB cable with two connectors, so the drive can siphon power off two ports simultaneously.
4) Use a proprietary connector.
So which one do you choose? Especially when your notebook only has a single USB port, and no room for any others?
Well, with Apple being Apple, they decided to go for super-slick engineering option number five.
They increased the amount of power to the Air's single USB port, over and above the USB specification.
Bingo. A bus-powed drive.
With issues.
The first is that since the drive needs more power than a standard USB port can provide, the Air's external SuperDrive can only be used with the Air. Nothing else has enough juice to run it, including a powered USB hub.
Which leads to the second problem. In order to be of any use, it has to be plugged into the Air's single, solitary USB port. Which means that nothing else can be plugged in at the same time. No printers, no external hard drives.
Nothing.
So what to do? Short of redesigning the drive.
Well, that's one option. In fact in an earlier article I suggested turning the drive not just into a drive, but a dock.
So what if we turned the drive into a combination drive/hub? Add four or so USB ports to the back so that we don't hog the Air's single USB port when it's plugged in. Add a small power brick to power the drive and the hub, which also means that you'd be able use it with other computers as well.
Apple could even make it a separate SKU, so that users have a choice of the existing version, or a "dock" USB hub version suitable for a desk at work or at home. Or someone else could build one as a third-party alternative.
The second option is even simpler, and oddly enough, is nearly the same as the one proposed regarding the Air's battery.
A cable.
Do a "Y" cable adaptor that the Air's SuperDrive can plug into, and that in turn can be plugged into a powered USB hub. Now we can plug the hub into the Air, plug the SuperDrive into two of the hub's ports, and regain the use of the SuperDrive plus whatever else we need.
So how about it? Any third-party suppliers willing to make one or the other?
And would you buy one if they did?
Secondly, they're basing this on information gained from the System Profiler, which is reporting power usage of 500ma. However, Profiler reports the same number if the drive is connected, reading, or burning a disk.
Which leads me to believe that it's simply reporting the USB maximum.
Next Up: The Ports
I read a while back that the USB standard has been enhanced with higher power modes.
See http://eetimes.eu/showArticle.jhtml?articleID=205602621 .
That is a USB charger chip by NXP allowing up to 1.8A.
So it seems that Apple maybe just implements one of the higher power modes
in the MBA USB port?
Also, currently my iMac (24" Alu) allows one 500 mA device from the keyboard USB ports,
so it also would allow more than 500 mA total: 500 + 100 + 100 (keyboard itself) = 700 mA...
My previous keyboards did not allow that.
Posted by: Pieter | February 17, 2008 at 02:47 AM