I have a dual boot system of Suse 9.2 Pro and WinXP in my AMD Opteron system with ASUS SK8N motherboard and 4 GB of RAM (4 sticks of 1 GB registered RAM). The original bios in SK8N (Ver 1.002) only saw 3.5 GB of RAM. This was attributed to Soutbridge resource allocation in ASUS's SK8N manual. Consequently both Windows XP and Suse 9.2 saw 3.5 GB system memory as well. I came across this newsgroup posting (http://lists.debian.org/debian-amd64/2004/04/msg00087.html) and I decided to update the bios. I updated the bios to ver 1.004 and then to 1.007 via two different bios flash methods per ASUS's instructions. Everything went smooth. Lo and behold, after doing the "Northbridge config: Remap above 4GB", the motherboard can infact see the full 4GB of RAM. Windows XP boots fine, however it sees 3GB of RAM. This is what I had expected originally from the 32 bit OS. On the other hand, when I wanted to boot into the 64 bit Suse 9.2, I get a kernel panic with a message saying: CPU 0: Machine Check Exception 4 bank 4: b2000000000070f0f TSC 3231cda3fc Kernel Panic - not syncing: Machine check I tried adding append="mem=2048M", "mem=3072M" and append="mem=4096M" one at a time in menu.lst of grub - but that didn't help. I did check the ram with memtest86 and all tests said that the ram is good, no errors. Things get complicated when I decided to reinstall Suse 9.2 pro. Now the installation from dvd hangs with a black screen. I read in a newsgroup that there is some issue with USB host controller in ASUS SK8N motherboard interfering with over 4GB RAM. http://lists.suse.com/archive/suse-amd64/2004-Dec/0089.html I tried disabling the USB controller but then my wireless USB keyboard and mouse combo is non-functional. I hooked up a ps2 keyboard and mouse, but my system still gives kernel panic during install. I went back to the bios and disabled the mapping of northbridge memory setting for 4GB. Now I can boot into Suse just fine, no kernel panic. Of course the system sees 3.5GB RAM. I would really love to use all 4GB of ram in my system since I paid for it. Any help or suggestion will be highly appreciated!