help with hardware upgrade & CFLAG options

[voltaic]

i am going to be upgrading my motherboard, cpu, and memory soon. i will be moving from an amd athlon 64 (using -march=k8 in my cflags) to a core2 duo processor (using march=prescott)
i would really like to have all my compiling done before i actually put the parts in so i can be up and running in a minimal amount of time, but i'm a little confused about the march option in cflags.

it seems to me that i686 will work for both of my configurations, however everything is currently compiled for march=k8.
i assume that the reason for having more specific march values is that there are particular optimizations that can be performed for a given processor that cannot be performed on the more general march=i686, and also may not exist for any other march value (for example, march=k8 has optimizations that march=prescott does not have, and vice-versa)

assuming this is correct, how should i proceed? i read about cross compiling in the gentoo wiki, and setup crossdev, and tried to create a new architecture (i686-pc-linux-gnu), but it quickly told me that it was "* Refusing to create a cross-compiler using the same target name as your host utils."
ok, that makes sense, duh.
so then, now that i know that, do i recompile everything on my system with a more general march=i686 and then recompile AGAIN once i get my new gear installed to march=prescott?
is the new gear going to be compatible with the march=k8 flag?
is the old gear compatible with the march=prescott flag?

ahh, the ramblings of a n00b
thanks for the help all!
_________________
Sam C Anderson

[snIP3r]

hi voltaic!

i think the action you are planning to do is not that easy. please do not forgett that even if you compiled your packages the right way, there is still an issue with the kernel you are using.
do you use the kernel that was installed while first time install??
or did you compile a new kernel with modifications?? in this case you should be aware of using the right hardware support in your (new) kernel config.

but lets go back to your initial problem: i would also proceed as you suggested: first compile the whole system with a morge generic arch (i686) and then after the upgrade with the new arch (prescott), i dont know exactly but i think the new gear is not compatible with the "march=k8" flag. same with the old gear.

i also remember that this case was discussed earlier here in the forum. have you found anything here about this issue??

HTH

snIP3r
_________________
Intel i3-4130T on ASUS P9D-X
Kernel 5.15.88-gentoo SMP
-----------------------------------------------
if your problem is fixed please add something like [solved] to the topic!

[voltaic]

yes, i have done some searching on the issue and come up dry. tried several different search terms.

i'm not particularly worried about the kernel, i have enabled all of the devices that i will have installed in my new system, and will look into telling the kernel that it will be running on a generic x86 architecture to begin with.
i think that the worst case scenario is that i have to boot from a livecd and chroot into my install and recompile the kernel in that environment.

i have already started compiling my old packages on one of the many different installs i have made (its a long story involving a newbie that knows just enough to be savvy, but not quite enough to get things done properly all of the time)

i am simultaneously trying to fix some problems with my first build of gentoo, so we'll see how it turns out.

this seems like something that should have a howto written for it in the gentoo wiki.
once i am all finished, and if i feel comfortable enough with what i have done, i will write one.
_________________
Sam C Anderson

[snIP3r]

hi voltaic!

ok, so i think all i can do is wish you good luck wir your "project"!

greets
snIP3r
_________________
Intel i3-4130T on ASUS P9D-X
Kernel 5.15.88-gentoo SMP
-----------------------------------------------
if your problem is fixed please add something like [solved] to the topic!