make.conf and building multiple kernels and worlds

Pieter de Goeje pieter at
Wed Jan 10 09:04:39 UTC 2007

On Tuesday 09 January 2007 17:21, Jonathan Horne wrote:
> i am finally looking at make.conf and how editing it could improve my
> system(s).
> 1) does specifying a cpu architecture really help?
It depends, but generally: yes. (although the perceived speed increase is 
probably marginal)
It really helps when you are using programs which use a lot of floating point 
operations. gcc is then able to use the faster sse2 instructions instead of 
plain x87 instructions.

> 2) if i am building for a p4-540 (nacona?), a p3, and a p4-xeon, what
> problems am i setting myself up for by specifying a cpu type on my build
> box?
You should choose the lowest common denominator: the p3 in this case. You'll 
run into trouble if you build programs for a new processor and then run them 
on an old one.

> at this point, im wondering how to go about building for more than one
> architecture effectively.  right now, i build one world, and 3 different
> kernels, but they are all build with generic options.
> just wondering how i can effectivly leverage my build server to have the
> best compile options for my target boxes.
> any suggestions?
The kernel probably won't be any faster, but in any case here's how:
#make CPUTYPE=pentium4 buildkernel

> thanks,
> jonathan

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