changing hardware, need advice

[dschobel]

I've got an athlon64 underway and plan to install that in my main devlopment box at the end of the week. The problem is that I'm currently running a P4 and have used the arch=P4 (or whichever is the usage flag which breaks compatibility with other architectures), so I'd like some advice on the best way to proceed.
Should I reemerge world now with with generic x86 arch flag and then once again with the AMD-specific one after I install the new proc? or would I be better off to just reformat and start anew?

[fangorn]

I just did the other way. I did a System build for an old Athlon 600 MHz on my new Athlon64. I just did a stage 3 install in a chrooted directory and compiled the system with march athlon and fed the world file as commandline input to the emerge command.

Unluckily this will not work for you this straight because youre P4 can't build a AMD64 system. What I would do is to install a stage 3 tarball on the new machine, copy the edited files of your /etc directory and your home directory to the new machine, edit the /etc/make.conf for CHOST and different USE flags, if you want do an emerge -e system, if you wanna save time do an emerge -uD --newuse system (basically to update the baselayout) and then take your world file, get rid of the newlines and copy it to the emerge commandline and take a long nap