Most Macs are engineered to last, and many of our Macs last much longer than is perhaps good for us. The three sub-units most likely to fail first and twist your arm to buy new are the hard and optical drives, which both have moving components that wear out, and the graphics card, which has been something of an Achilles heel due to the use of lead-free solder.
If your optical drive starts to play up, not recognising disks, and does not recover after a very careful gentle clean, you might be tempted to try a neat little Apple USB Superdrive – an accessory which you may already have to accompany a MacBook, perhaps. Although the Superdrive works fine with all models released after 2008 if they do not have an internal optical drive, it will not work with any Mac which shipped with an Apple internal optical drive.
For a straightforward USB device, this may appear odd. And it is odd, because if you follow the instructions detailed by Luz, you will see that the drive can be enabled in software.
So all the way along, Apple could quite easily have allowed all those with Macs released after 2008 to be able to use its Superdrive as the default, without having to fiddle with /Library/Preferences/SystemConfiguration/com.apple.Boot.plist
Except that now, with El Capitan’s System Integrity Protection (SIP) and rootless configuration, users are prevented from making that small change which would allow Macs with internal optical drives to use the Superdrive. It might be possible to restart in Recovery mode, open Terminal, turn SIP off, restart, then edit /Library/Preferences/SystemConfiguration/com.apple.Boot.plist to enable the Superdrive, restart in Recovery mode, open Terminal again, turn SIP back on, and finally restart normally. But so far no one seems to have tried that, or if they did they are still recovering from the task.
If your Mac is still supported by Apple, and they have stock of replacement optical drives for it, you can of course pay to have your duff internal optical drive replaced. It is not a difficult task, but the replacement kit requires a couple of plastic baffles, which are needed to keep dust entering the open slot from getting drawn into the inside of an iMac, for instance.
But if your Mac has been deemed obsolete, and Apple no longer has any replacement optical drives for it, the easiest solution is to replace it with a new Mac, and that is clearly what Apple wants you to do. The ironic twist here is that your new Mac will not have an optical drive in any case, so you will then need to buy – yes, an Apple USB Superdrive, which cannot be used with your old Mac because you can’t flick the software switch to enable it, because of El Capitan’s security systems.
All this leaves a rather bad taste in the mouth, doesn’t it? Enforcing obsolescence by engineering your system software to prevent users from dealing with ageing components, is not the sort of behaviour we expect from a caring, customer-oriented Apple. It is thoroughly bad Apple.