[Spivak]

But you would add an 's' to both of your examples to make two central processing units (CPUs) and two solid state drives (SSDs). I agree, it's a weird rule but it certainly sounds better.

When the pluralization happens in the middle of the acronym it becomes weird -- one FLOPS, two FLOPsS?

[mikeash]

Both of my three examples?

Anyway, you're right, they would all get an S at the end either way.

A better example would be "captcha." You'd say "two captchas," not "two captcha" or "two captscha."

For a less polite example that works the same way, consider MILF.