CPU's are suspect too. Security researchers are buying Russian 486DX clones from the 90's, since that's believed to be the last known processor that isn't tampered with. Prices on these have skyrocketed.
Any newer CPU can be tampered with in undetectable ways.
See: https://www.schneier.com/blog/archives/2013/09/surreptitiously.html
Biting the hand that feeds IT
