24-inch iMac not as 3D-upgradable as you might think

We've seen some reports around the Web that has an upgradable graphics chip. It started at MacGeneration (in French). The story is indeed correct, but in order to clear up any confusion about what it means, we thought we'd clarify.

First, Apple confirmed for us that the new 24-inch iMac does use Nvidia's MXM mobile graphics chip interface, which means that the graphics chips are technically swappable. This is a cool feature that's popped up in a few laptops already, and it's beneficial because it gives system vendors an easy way to add different graphics chips to mobile and mobile chip-based (such as the iMac) systems. If you upgrade the 24-inch iMac's default GeForce 7300 GT chip to the more powerful GeForce 7600 GT, the MXM interface makes it simpler for Apple to make that change at the factory.

But MXM doesn't mean that you can upgrade the iMac's 3D chip on your own the way you might on a desktop. For one, Apple doesn't provide access to the slot. We haven't seen a 24-inch iMac ourselves yet (soon), but Apple told us that, unlike upgrading the memory, which is easy on an iMac thanks to a small hatch on the bottom of the unit, there is no external access to the iMac's MXM slot.

And while we concede that such a limitation might not stop a determined hacker, even if you could access the MXM slot without damaging the system, you'd be foolish to try. The reason is that there are no MXM-based chips for you to purchase to upgrade to. You can upgrade the 3D chip on Apple's site prior to purchase, but NewEgg isn't selling a stand-alone, MXM-based GeForce 7800 GT card. Nvidia told us that it hopes a mobile 3D chip upgrade market will emerge eventually, but it's not there yet. For now, MXM is really only a direct benefit for system builders.

So, sorry, would-be iMac 3D chip upgraders. You might be able to swap out MXM chips at home someday, but not now, and not on this iMac.