How does your Thunderbolt port go?

By and large, Apple’s products are well-designed and well-engineered. But every now and again, appearance gets the better of good engineering sense, and something isn’t right – in this case, the Thunderbolt ports on iMacs.

Like most modern plug-and-socket systems, Thunderbolt relies on the rectangle. It is slightly squarer than USB’s, but Thunderbolt’s sockets are significantly shallower. Mount a Thunderbolt socket with its long axis in vertical alignment, and you end up with a connection which is not as stable as it needs to be.


Laptops don’t present this problem. Because they’re engineered to make the case as thin as possible, all their sockets have their long axes horizontal. The Mac mini and Mac Pro also opt for the same orientation, but for some strange reason the USB and Thunderbolt sockets on iMacs are different.

If you care – when your iMac is shut down, of course – to brush your hand past a Thunderbolt cable connected to a socket on the back of an iMac, you’ll notice that the plug can wiggle in the socket. Different cables, with slightly different plugs, vary in this. I had not realised just how insecure the Thunderbolt connections are on the back of my iMac until one day I was a little ham-fisted when reaching over to disconnect an adjacent USB plug. I almost dislodged the Thunderbolt cable next door.

I don’t know why Thunderbolt sockets are so much shallower than USB sockets, although I suspect this may be to facilitate their use in tight spaces such as Apple’s vanishingly thin laptops. But that, combined with their orientation on iMacs, makes them worryingly insecure. In fact, they seem to be the weakest link in my RAID backup system.

Maybe this year’s new iMacs will change that.