I have a very old installation of 32bits Debian running in new hardware. Until now running a 64bits kernel was enough to use efficiently more than 4GiB of RAM. The only problem I found was the proprietary drivers from AMD/ATI and NVIDIA, that did not like this mixed environment and some problems with openafs, easilly solved with the help of the package maintainers of openafs. Crossgrading the Qemu/KVM to 64 bits did not pose a problem, so I have been running 64bits VMs for some time.

But now the nouveau driver do not work with my new display adapter and I need to run tools from OpsCode not available as 32bits. So is time to do a CrossGrade. Finding some problems I can not recommend it to the inexperienced people. Is time investigate the issues and report bugreports to Debian were appropriate.

If you run 32bits Debian installation you can easily install a 64bits kernel . The procedure is simple and well tested.

dpkg --add-architecture amd64
apt-get update
apt-get install linux-image-amd64:amd64

And reboot to test the new kernel.

You can expect here more articles about crossgrading.