On 1/8/23 17:36, hede wrote:
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
Thank hede! you solved my problem! i enable Memory hole Remapping in
bios, memtest86+ shows 4095M memory now! top in buster for 686 shows
3029.6M while top in bullseye for amd shows 3930.9M. Thanks!
