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Will an external SSD speed up my old PC?

Q I’ve been investigating external SSDs and have read that they do exactly the same as internal SSDs. I have a never-so-slow HP Pavilion 23 all-in-one PC and am reluctant to open it up. So, I wonder whether what I’ve read is true. Could you please explain?

Dr UCHutter

A On the one hand, this is true. On the other, it’s codswallop.

The basic components of any two SSDs are the same, regardless of whether they are designed for use inside or outside of a computer. So, in that regard at least, yes – all else being equal, an internal SSD is much the same as an external model.

However, all else is unlikely to be equal. For starters, any drive you connect internally to your PC is likely to use a SATA interface, while an external drive will usually attach via USB. There are multiple different generations of each of these interfaces, not to mention different specification subsets within each generation.

For reasons of space we'll have to greatly oversimplify here. But, suffice to say that, on an older PC like yours, the internal SATA interface’s data bandwidth will almost certainly be more than that of the USB ports. In other words, if two otherwise-identical SSDs were connected via SATA III and USB 3.0, the SATA-connected drive would perform better than the one hanging off USB 3.0 – because the USB 3.0 interface would present a bottleneck.

The SSD’s storage chips could work faster than the bandwidth available on USB 3.0, which tops out at 5Gbps (compared to 6Gbps of the SATA III interface your old PC probably has).

But it’s not even as simple as that, because it is unlikely that an SSD connected via USB 3.0 would ever have the luxury of making use of the full 5Gbps bandwidth, because that’s a theoretical maximum – and any number of other