> Running them on in-order, speculation-free hardware would be quite sufficient. In-order isn't a magic bullet against Spectre, they still do spectulative exec

> Running them on in-order, speculation-free hardware would be quite sufficient. In-order isn't a magic bullet against Spectre, they still do spectulative execution after predicting branches and they can still be vunerable. ARM have listed at least one of their in-order cores as vunerable. To be free of all speculation you have to go back to the 486, which didn't even have branch prediction. Besides, if you are making custom CPUs there are other options to avoid Spectre that don't require eliminating all spectulative execution.