sometime 15+ years ago a virus that simply melts the CPU was impossible but I opened the theoretical concept that it may one day be done my friend called it the "armageddon" I'm not sure if Spectre and Meltdown does what I think it does if my pre-conceived notions still held true I guess like War, Computers never change and this was largely a time Windows XP was the mainstream OS damn I feel old
Whilst obviously bad things, and bad for Intel --- although it makes not a lot of difference to them since they will still make most cpus --- I would take heart from the terrible HeartBleed bug, which was all the fault of Open Source, destroying the entire internet and ravaging the Armageddon landscape left behind for decades.
Or maybe not. Security writers are paid to be even scarier than this little ghost.
Meltdown and Spectre are exploits any hacker could use to run a parallel process and read other process data. This could lead, for example, to run javascript code and access your browser's passwords. Before the patch the exploit wasn't publicly known, but now that it has been released a hacker could theoretically reverse engineer it and know about the exploit, then use it against unprotected CPUs.
You can't burn a CPU unless the hardware is failing. You could maybe deactivate security sensors and let it burn, but it's a long term process and would involve a really specific hardware with a specific OS to do that. Impossible for a massive attack.