I’ve observed the same behaviour on my zx2000, but not on my rx2620 on which I was able to install wheezy without issue several months ago. Given that my 2620 only has two Madison 9Ms in it, I don’t think this is a CPU instruction/feature set issue but an Kernel/EFI interaction related one. (EFI on the rx2620 is newer)
That said, my ia64 specific knowledge is only minimal, I guess I’m going to do a lot of learning now. C. -- Chris Collins