I have ASUS P5Q Pro mboard with 8 GB ram, (4 x 2gb sticks). Memory remap enabled. Installed 64bit 12.04 ubuntu. Often restart or shutdown or boot would hang within ubuntu. BIOS says I have 8192MB. Memtest 86+ fails with 8GB and memory remap enabled.
If I disable memory remap bios says I have 7423MB, memtest does not fail and ubuntu 64bit boots, shuts down and restarts every time. System settings say I have 7.1GB RAM.

If I use just 2 x 2GB sticks with memory remap enabled or disabled then there are no issues with OS & bios and system settings see 4gb. I have changed RAM, moved to different slots, no change.

I also have ubuntu (32bit) 10.04, this boots with memory remapped enabled or disabled

Why does enabling remap not work with 12.04?