On an EM64T box suffering from bug 116766, I attempt to boot with mem=2G mem=4G etc. In all cases, isolinux appears to corrupt the initrd, as the kernel a) says it's mounting an ext3 fs as ext2 b) fails to read the filesystem well enough to run init/loader Booting without mem= works. Box has 4G of memory, with a hole that makes .5 GB appear from the 4-4.5 GB mark.
Wonder how this works with initramfs.
Will reopen this if it ever becomes a problem again.