updated 09:39 pm EDT, Wed July 18, 2012
Appears to fix USB 3.0 external drive mounting issues
Responding to complaints about CPU power use under load that eerily echoes a 2011 issue and also resolving a tricky issue regarding some USB 3.0 drive enclosures, Apple today issued a software update for just the latest models of MacBook Pro and MacBook Air. The "Pro Update 1.0" release notes do not specify the power consumption and USB problems in any detail, but reports of the machines losing battery while under high load even while plugged in have been spotted in support forums.
A more common issue has been what exclusive testing by MacNN Labs found was a chipset-compatibility issue between some brands of USB 3.0 drive enclosures and the latest MacBook models. On some enclosures -- mostly low-end and no-name models -- the negotiation of signals that tell the drive and the MacBook to run the device at full USB 3.0 speed failed, causing drives not to mount or in some cases not to remain mounted reliably.
The lab tested two of the latest models of Retina MacBook Pro and one of the new MacBook Airs, along with over 30 name-brand and lesser-known enclosures. We found that the Retina MacBook Pros were more finicky about low-end USB 3.0 enclosures than the MacBook Air. When forced down to USB 2.0 speeds, all enclosures worked fine with all the new Macs, suggesting a bridgeboard chipset issue reminiscent of the Firewire mounting problems with external cases seen a decade ago.
In our test, timing issues appeared to be the main culprit causing the Macs not to utilize the USB 3.0 speeds. If the new update loosens the timing window, lower-end chipsets should be able to mount and run reliably at full speed. Name brand enclosures such as those from LaCie and Other World Computing were found to be completely solid at USB 3.0 speeds in our testing.
Preliminary testing done late Wednesday suggests that the new software update does resolve these issues. MacNN will run further tests and update this story if necessary.
The Pro Update, despite the 1.0 name, is actually the second software update the latest models of MacBook Pro and MacBook Air have received since their mid-June debut. The previous updates lacked the "Pro" name in their titles, and were issues within a day of the debut. The file for the latest update is 76.64MB, and will show up in affected owners' Software Update program and can be downloaded directly from Apple's support site.
An earlier version of this article suggested the new update did not fix the USB 3.0 drive issues. This has been corrected. MacNN regrets the error.