> I added code to the Linux startup sequence that ignored everything the BIOS said about memory maps, queried what physical DIMMS were there, and rebuilt my maps by hand.
I'd love to see this code; doing memory management entirely in the OS and ignoring the BIOS sounds like fun (modulo working around BIOS-specific memory reservations so the OS doesn't get its memory stomped on by the BIOS).
I spent some time last year running various scripts to get an NVIDIA GPU working over thunderbolt in windows on a macbook pro. The problem is the DSDT table in many macbooks doesn't allocate enough space for pci-e devices. The NVIDIA driver in windows tries to allocate memory via that table to talk to the eGPU and it fails.
For some reason it works fine under MacOS - either macos ignores the DSDT table completely, or it allocates memory a bit differently than windows. In any case, the answer is to use obscure tools to download and patch the DSDT tables to allocate more RAM toward PCI-e. Doing this through UEFI feels very magic.
I don't know why so much of this stuff is up to the hardware vendor. Maybe there's a good reason, but I would expect the windows memory manager could do a much better job if it didn't have a bunch of memory range sizes hardcoded by apple.
I'd love to see this code; doing memory management entirely in the OS and ignoring the BIOS sounds like fun (modulo working around BIOS-specific memory reservations so the OS doesn't get its memory stomped on by the BIOS).