[?]"multi-arch" system possible?

[wsh]

Hi, i have to build a gentoo system in a HD that has to be used in an amd and a x86 computer for a school project(in my school there are dual cores, or core 2 not sure, and at my home i have a Phenom II).
This must been done like this, because it's a school project that sometimes will be developed at school and sometimes at home.

My question is, if its possible to build a system that is compatible with both processors at the time of emerging. I don't need any optimizations, so i was wondering if leaving the cflags as "i686" or something else would leave the system ready to work in both procesors.

And what stage is recomended, amd64 or x86.

Thanks a lot, and sorry if my way to speak english is not the best.

[jerann]

Personally, I'd use i686 and do a 32-bit build. It sounds like your school computer is probably 64-bit capable (Core Duo, Core 2 Duo, and I think some Pentium D/Pentium 4 varieties were), but really you don't get much of an advantage with 64-bit most of the time anyway. If you think you'll use this hard drive in something with more than 4 GB of RAM, then 64-bit would be a must, but most of the time 4 GB is sufficient. If you decide to go with 32-bit, i686 should be perfect as long as you know you won't be running that install on anything older than a Pentium II (that is, anything before around 1997).

The kicker is that if you get a 32-bit install going and you later want to upgrade to 64-bit, you'll have to reinstall from scratch. So, if you want to go with a 64-bit build, you'll first want to make sure that your school computer supports 64-bit instructions. You can do that by looking up the processor specs on whatever OS you're on (you'd go to System Properties in Windows, or just type cat /proc/cpuinfo at a console in any version of Linux), and check it at Wikipedia or something like that. Then, during the install process you'll eventually get to the point of setting up /etc/make.conf. I'd be willing to bet that Phenom II will probably run anything compiled for an Intel 64-bit processor of the generation we're talking about; that is, if you used -march=nocona, it would probably work. A brief glance at Google and the gcc documentation didn't say that explicitly though, so if you really don't care, you could either:

1. Don't use -march at all in your CFLAGS; instead, just put CFLAGS="-O2 -pipe"
2. Don't use -march, but throw in a few instruction sets you know will be there: CFLAGS="-mmmx -msse -msse2 -msse3 -O2 -pipe"

I'm going to disclaimer all of that by saying I haven't ever tried to do this myself, but I'm reasonably certain that a Phenom II and an Intel x86_64-style processor are close enough that gcc should be able to compile optimized 64-bit code that will run on both. The most important thing is to decide before you get started if you're going to do 32- or 64-bit, because that will affect which install media you use, and which handbook you use.

[wsh]

At my school there are E2200 or similar. They support 64 bits.
I won't be using more than 4gb, so i got a i686 finally.

I'm having some sort of problems with the amd64 build that i have at home like java not working and flash working weird, i have just 2gigs of ram, it's a good option to build an i686 with the optimizations of my Phenom II?

PD: I edited the post

[jerann]

32-bit might be easier... I don't develop in Java, but I the last time I tried (a year or more ago), I had trouble getting Java to work in 64-bit Linux. And actually, I don't use Opera either; lol. Otherwise, I haven't had any trouble at all on 64-bit. But since it doesn't look like you'll get any appreciable benefit from 64-bit, I'd redownload and do 32-bit, just to be easy.

[wsh]

[wsh]

Hi again, i got to the part when i set up X.

I got it working at home where i have an ATI vga.
But at school all the vgas are nvidia.

Is there any way that i could use X in both systems?
Maybe using 2 different xorg.conf?

I installed nvidia-drivers, but i don-t think that X would load the nvidia module automatically.

Any ideas?

[Flarkis]

what does your xorg.conf look like? and are you running x86 or ~x86?
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