I was hoping to see that someone had gotten an AMD system booting with 8GB or more of ram but no cigar. Judging from the 10.5.7 HCL list -
others in addition to myself cannot get 8GB of ram booting on AMD motherboards under leopard 10.5 because of a 64 bit issue. It almost boots but hangs just before the final display of the desktop. 6GB boots but many installs will fail such as the iDeneb 10.5.7 upgrade and Final Cut Studio 2. Hopefully Snow Leopard will allow AMD users to break the 4GB barrier.
Now I use the maxmem=4096 flag on my 8GB dual boot system so I can boot into 4GB with OS X and 8GB with Vista 64.
I have an amd64 6000+ running on a sb600 motherboard from a gigabyte GA-M69. I have 8Gb of ram and I think that the kalyway 10.5.2 reserves all of my memory. Whenever I use vmware fusion I can reserve as far as 6 gb for virtual machines and still I can have and decent running leopard. The same thing happened after installing leo4all 10.5.4 and upgrading to 10.5.8. It is strange though that chess witch is a 64bit application says that it is running in 32bit mode. The info though says that I have 8gb of ram.