Am 08.01.2023 00:30, schrieb Jeremy Hendricks:
I imagine it’s a bios limitation and it cannot address the full 4GB even though it’s a 64bit CPU. This was common with the Intel 925/945 chipsets even through they supported Intel 64bit CPUs of the time.
I'm pretty sure it can address 2^32 bit aka 4 GB. But within this range there is the PCI address space. PCI cards are memory mapped. To access memory regions on PCI devices you can simply access main memory. But you cannot access PCI devices AND use full 4 GB of physical main memory within the 2^32 bit range.
Typically Chipsets/BIOS can map the missing memory somewhere above 4 GB but not every Chipset/BIOS does this. Then even in 64 Bit mode you'll lose memory in the range of the PCI address space. If, on the other side, the Chipset/BIOS maps those memory regions above 4 GB then even in 32 Bit Mode Linux can use this memory (via PAE).
hede
