[p0ckets]

Until consumers demand this as a requirement, it won't happen. Almost everyone would rather have a compiler/language/OS/ISA/CPU that's finishes faster some of the time, rather than one that finishes at the same time all the time. It would just appear (especially in benchmarks) to be slower for no apparent benefit.

Maybe we can introduce a new set of instructions that are guaranteed to be constant time, but good luck convincing the compiler/language/OS to use these slower instructions even if just for the code that is important for security.

[p0ckets]

And for this particular attack, constant time isn't even enough! You would need either constant power, or limit the frequency when running secure code (which again reduces performance).

[Atheros]

Constant time comparisons take practically no time at all. I hardly see how it would noticeably reduce performance if software could command a CPU to lock to a low frequency for a certain period of time or when the sensitive code finishes, whichever happens first. The OS could track how often this happens and give a simple UI so that we can blame those applications that abuse it.