That happens too. Prime 95 and other stability tests are used and can check when wrong results are returned. There's often a sliver of frequencies where a system under load begins performing floating point calculations incorrectly while other, simpler systems in the CPU are still functioning correctly.

The BSOD, oops, or panic is a symptom of widespread errors.

That's also possible. That's why overclockers run Prime95 to test their CPU stability.

Also, a BSOD or panic in the wrong time can cause massive data loss. That's beyond bad sometimes.

Edit: I mixed Prime95 with SuperPi. Thanks AaronFriel.

Why do you think the panic happens?

It's because the code does the wrong thing, and that happens silently... until it hits some pointers or kernel structures and stops being silent.

Not always. CPUs have extensive "machine check" capabilities. some of these MCE events are recoverable, some not.

If the processor fires an unrecoverable MCE event, you're frozen with a nice, explanatory panic.