# SMP advice

## nitro322

I'm planning on building a dual-Athlon box soon, but due to budget constraints I'll probably only be able to put one processor in it initially (I'm hoping to add the second processor with a month or two).  If, when I install Gentoo, I enable SMP support in the kernel and build everything with just the one processor, will everything automatically work (ie., take advantage of) the second processor when I add it?  Or will I need to recompile everything?  Thanks.

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## rac

 *nitro322 wrote:*   

> If, when I install Gentoo, I enable SMP support in the kernel and build everything with just the one processor, will everything automatically work (ie., take advantage of) the second processor when I add it?  Or will I need to recompile everything?

 

Most application software does not even know (or need to know) how many CPUs you have; all of that is generally handled by the process scheduler in the kernel.  So there should be no need to recompile usermode software.  You will be putting a small amount of unneeded overhead on your system running an SMP kernel on a uniprocessor system in the meantime, but it shouldn't be significant.

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## delta407

I would suggest simply building the kernel for SMP, that way if you put in modules (nvidia-kernel, alsa, etc.) you won't have an extra hoop to jump through once you get your new CPU. Either way, though, it's not that bad. (Rebuilding kernels on an Athlon isn't as hard as rebuilding them on a 386, believe you me.  :Wink: )

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## nitro322

Thanks for the info.  I'll just go agead and setup everything for SMP in advance, and then jut drop in that extra CPU when I get it.  Don't think the overhead should hurt too much on an Athlon MP 2000+  :Very Happy:  .  Actually, I might go ahead and recompile everything when I add the second processor anyway, just for the pleasure of watching everything zoom by.   :Wink: 

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