TidBITS reader Jim Griffiths recently tipped us off to a widespread issue with SuperDrives: the inability of some drives to read or write to discs. In his particular case, a MacBook Pro began having difficulty reading all kinds of optical discs shortly after its warranty expired. This led him to start a thread describing the problem in the Apple Support Discussion forums.

As of this writing, that thread now contains over 225 messages and has been viewed over 30,000 times. Those are big numbers for the forums - and in fact a similar thread has garnered more than 19,000 views - and indicate that Jim is far from the only one experiencing this problem.

While combing through the posts reveals an unusually high number of failing SuperDrives, the symptoms, causes, and solutions offered don't add up to a clear picture of the situation.

Symptoms and Variables -- These SuperDrive-related problems evince a few common symptoms: at some point, a user's optical drive fails to mount optical discs, usually ejecting a disc after a short period of attempting to read it. However, the systems affected, discs affected, and timing of the symptoms' arrival differ among users.

According to discussion forum posts, affected systems include the MacBook, MacBook Pro (13-, 15-, and 17-inch), MacBook Air, iMac and Mac Mini. The systems range in age from early 2006 to late 2009.

Specific optical disc drives that have been identified on the forums include:

• HL-DT-ST DVDRW GSA-S10N (the most commonly listed)
• HL-DT-ST DVDRW GWA-4080MA
• MATSHITA DVD-R UJ-85J
• MATSHITA DVD-R UJ-846
• MATSHITA DVD-R UJ-857E
• MATSHITA DVD-R UJ-857D
• MATSHITA DVD-R UJ-867
• MATSHITA DVD-R UJ-868
• MATSHITA DVD-R UJ-875

Affected disc types vary: some users are able to mount DVDs but not CDs; other users, vice versa. Some are able to mount commercial CDs and DVDs, but not blank CDs and DVDs, and vice versa. Some are able to mount everything but blank CD-Rs, while others are able to mount everything but blank DVD-Rs. Some are unable to mount any disc of any kind. Some find the issue is intermittent, while others find it constant.

When these problems start happening for users varies as well. Some users noticed problems with their SuperDrives from the start, others say things started going screwy after a couple months, many others complain symptoms didn't appear until just after the 1-year warranty expired, and still others claim problems appeared only after Snow Leopard had been installed.

This breadth of dates, affected drives, and related disc types makes isolating the problem extremely difficult. It's possible - even likely - that the problem is actually a variety of problems. Or it might be a single problem with a variety of triggers, leading to variable symptoms and start dates.

Unfortunately, it's devilishly hard to pin anything down based on anecdotal reports from users, especially in this case. For example, the reported timing of a problem's arrival is dependent on the user's awareness of the problem. For instance, if a user's SuperDrive was dodgy from day one, but wasn't used with a problematic disc type until a year later, the user might report the latter incorrect date as opposed to the correct date as the problem's origin.

Similarly, the great disparity over which discs can or can't be read may point to different problems, one problem with inconsistent symptoms, or inconclusive testing by users. If a user tries only commercial CDs and DVD-Rs, he may report that those discs don't work and make assumptions about other discs or simply not report on them - skewing, or at least complicating, the data.

Causes Offered -- Given these symptoms, users have been putting their heads together, talking with Apple Geniuses, and consulting with other knowledgeable techies to arrive at some possible causes. As you might imagine, there are a variety of suggestions.

The basic debate seems to boil down to whether we're looking at a hardware issue or software issue. Some users believe the problem is simply rooted in faulty optical drives, while others are convinced problems were prompted by a recent firmware or security update.

A smaller group of users on the forums believe the installation of Snow Leopard is to blame, though many others are quick to point out that these problems have existed long before Snow Leopard.

Those arguing against faulty hardware as the underlying cause point to the fact that a wide variety of Macs and drives are affected. Supporters of a software-based theory are also usually convinced that their specific problems began only after a major software update (though there's no consensus regarding which update might have caused the problem). A common argument is that it's possible a faulty update could have lowered the operating system's tolerance to dirt or dust on a disc.

Another user argued in support of a software cause when he found he was unable to mount a disc on his Mac even when using an external optical drive. When he moved the same external drive to a Windows machine, it worked fine.

As both symptoms and the arrival of the symptoms seem to vary, the efforts to pinpoint a single underlying cause haven't gotten far.

Solutions Offered -- Despite ongoing debate over the causes of the problems, many solutions have been proposed. Below is a list of fixes suggested by forum users, all of which offer unpredictable degrees of success or failure.

• Purchase and employ a DVD/CD drive cleaning disc. These discs are designed to remove dirt, dust, and static buildup from your optical drive. Alas, most users who tried this solution found that the cleaning disc would be ejected before it could do any good.
• Use a can of compressed air to blow inside your computer's optical disc slot and clear away any built-up dust. While several users found this solution helpful, others claimed it didn't eliminate the problem, and at least one user found it actually made the problem worse - rendering him unable to insert a disc at all.
• One user recommended tapping right above the disc drive as it begins to slow down its reading prior to ejecting the disc. While this one user swore by this solution, others found it had no effect and, frustrated, suggested that tapping with a hammer might relieve more stress.
• Several users found that repairing permissions in Disk Utility and resetting PRAM/NVRAM cleared up their issues, though many others said this produced no positive effect for them.
• One user, whose discs weren't being ejected but instead simply weren't mounting, found success by changing the default system behavior for when a disc is inserted in the CDs & DVDs pane of System Preferences.
• Several users said that opening Disk Utility prior to inserting a disc solved their problem, though again, success with this solution wasn't widespread.
• Most - but not all - users who had their SuperDrives replaced - either under warranty from Apple, by paying out-of-warranty fees to Apple, or by doing it themselves - found their problems went away. Some reported needing multiple replacements or even a logic board replacement before the problem disappeared.
• For users whose machines are out of warranty, buying an external optical drive is a cheaper option than replacing the internal drive. Though, as mentioned above, at least some users found that they were unable to read discs even when using an external drive.

Summary -- While the symptoms and solutions for these issues vary widely, they all revolve around the SuperDrive. If you are experiencing issues similar to the ones described above, consider adding your experiences to the ongoing forum thread linked at the start of this article or contacting Apple (either online, or by working with an Apple Genius at a retail store) to voice your concerns. We'll continue to monitor this issue, and we hope that Apple will take steps to correct it.