justamacguy wrote:
Hard drives have a much more common failure rate than every 5 years.
Not in my experience. I still have old HD's I extracted from long dead Macs & all of them except one still works fine. OTOH, I do not have one Superdrive built into any of my iMacs that doesn't have some sort of problem, ranging from not being able to read disks when they are first inserted to not reliably ejecting them.
And the argument that putting an optical drive in the iMac would screw up the cooling of the machine is bogus too. There is no reason the machine can not be designed to cool adequately with one in it...
Yes, that could be done, but not without significantly increasing the noise the higher capacity cooling system generates. You have to check out one of these new iMacs in person, preferably in a quiet room, to appreciate just how quietly they run. If you run one really hard for 30 minutes or so, in a very quiet room you might just barely be able to hear the fan, but probably not.
The other design problem with this is the more heat producing things you put in the case, the more air you have to design the cooling system to be able to draw into it to cool them. Not only is that noisier, it draws in more dust, so you have to design the system to be able to handle that without clogging up anything & producing a hot spot that would significantly increase the risk of component failure. That means using bigger & more complex air ducts & shrouds, & bigger case vents with larger unobstructed openings ... which in turn allows more operating noise to radiate from the case, even when the extra cooling capacity isn't needed.
You also have to make sure that any optical drive you put inside the case is well sealed to prevent the cooling system from drawing dusty air into it through the disk insertion slot. That in turn means it will heat up more when in use (because the heat producing parts like the laser are sealed off from cooling air). And that in turn limits the maximum burn speeds you can use (because the faster the burn speed, the more powerful the laser has to be & the more heat it generates). If have ever wondered why Apple has never offered faster than 8X Superdrives, that's one of the reasons.
Do you see where this is going? Every design decision is a compromise among mutually conflicting goals. You can't maximize them all; the best you can do is carefully balance the compromises so everything is within acceptable limits. That's what good design is all about.