Meltdown does not rely on speculative execution; it exploits only out-of-order execution.
1. Internet-of-things ecosystem cannot be attacked using any hardware-software exploit because it is too diverse for the attacker.
2. Software Trigged Hardware Trojans can be used to cause denial-of-service (DoS) attack.
3. Preventing the execution of the clflush (cache flush) command can deter all types of Rowhammer attacks.
4. During a Spectre exploit, once the processor starts to perform speculative execution, it gives the attacker theoretically unlimited amount of time to finish the attack.