alt Hacker NewsThere would also be a block of memory mapped hardware registers also needing address space that you have to poke to make the GPU actually do GPU things, instead of just being an expensive way to add extra memory to a system, no?
And if my experience from embedded development is in any way transferable, they're probably fairly spread out and probably takes a fairly big chunk of address space too.
Yes, typically the memory mapped memory is in one (64-bit) bar, memory mapped registers in another (64-bit) bar, plus for compatability with vga, probably a 32-bit memory bar and an i/o bar. 64-bit bars take up two bar slots, so that fills all six slots in the PCI config.