5 ms·
> Why would we want to switch to 128 bit addresses? How else are you going to have more than 16 exabytes of RAM?
by imron 7y ago
> Why would we want to switch to 128 bit addresses?
How else are you going to have more than 16 exabytes of RAM?
- eru 7y agoExactly, you probably won't. And I don't mean that in an absolute sense. People might very well get up to those orders of magnitude of RAM; but you are unlikely to have that amount of RAM available to a single processor. The extra margin of the 64 bit might help with address space randomization, though.
- jagger27 7y agoMemory banking is the obvious and ancient solution. PAE is another.
- amluto 7y agoPAE is a kludge because the architects needed to add another tiny page table level to keep 32 bits of virtual space, but didn’t really want to add another level. The concept of having more physical address bits than virtual bits is reasonable, although it falls apart a bit with virtualization. The idea of having magic registers that fill themselves in for you and can’t be read at all (such as the PAE PDPTR registers) is a bad idea that unfortunately repeats itself in x86 design. Architects: don’t do this.