"Real quick" is human speak. For large amounts of memory it's still bound by RAM speed for a machine, which is much lower (a couple orders of magnitude I believe) than, say, cache speed. Things might be different if there was a RAM equivalent of SSD TRIM (making the RAM module zero itself without transferring lots of zeros across the bus), but there isn't.
I'm completely unfamiliar with how the CPU communicates with the memory modules, but is there not a way for the CPU to tell the memory modules to zero out a whole range of memory rather than one byte/sector/whatever-the-standard-unit-is at a time?
As I type this, I'm realizing how little I know about the protocol between the CPU and the memory modules--if anyone has an accessible link on the subject, I'd be grateful.
That's what I referred to as "TRIM for RAM". I'm not aware of it being a thing. And I don't know the protocol, but I'm also not sure it's just a matter of protocol. It might require additional circuitry per bit of memory that would increase the cost.
'trim' for RAM is a virtual to physical page table hack. Memory that isn't backed by a page is just a zero, it doesn't need to be initialized. Offhand it's supposed to be before it's handed to a process, but I don't know if there are E.G. mechanisms to use some spare cycles to proactively zero non-allocated memory that's a candidate for being attached to VM space.
