[bogomipz]

I'm not sure there's any qualification for how much rack space or form factor HSM an HSM uses.

For instance the YubiCo HSM is just a USB device that plugs into a server.

[danpalmer]

Sure, I did say "typically". Obviously the form factor does not define an HSM, but in general the term is used to refer to dedicated machines designed for high performance at scale with a large number of users, rather than a SmartCard/USB device which is, typically, for a single user.

[bogomipz]

I see, that makes sense. Cheers.