* Marvell mv78xx0 and kirkwood (armv5 pj1) were fairly
  powerful in 2008 and could support at least 1GB of RAM,
  but I only found one machine (OpenBlocks A7) that does
  this. It's unclear if anyone is still updating kernels
  on this machine, but they could /probably/ use
  VMSPLIT_3G_OPT if they do.

If i remember correctly, there was a design issue with the OpenBlocks
A7, and it would not run with its full amount of memory. To get a
stable system you had to limit the RAM. I don't remember if that was
just with the NULL series, and it was fixed for mass production
devices, or they are all broken.

I doubt there are any mv78xx0 machines left, why where never very
popular, but there are still Kirkwood NAS boxes around. I keep mine up
to date, put an LTS kernel on it once a year, update to the latest
debian sid.

	Andrew