I have a desktop with AMD AM@ dual processor and thinking of up grading the processor to a quad core.

The MB Asus M3N78 is AM3 compatible.

Can I just unplug one CPU and plug in another or would I have to reinstall the operating system.

Thanks for any help

Assuming that the motherboard has the latest bios and does in fact support quad-cores (update your bios before swapping!--the motherboard should support the new chip but better safe than sorry) Ubuntu will have no issues with the change.

Case in point; my old laptop went kaput on me. I moved over the cpu and WLAN card into a new ITX motherboard with a whole different northbridge (went from Intel->Nvidia), RAM (went from DDR2->DDR3), graphics (both Nvidia but different models), etc. and the sucker just booted right up. Well, except for the Windows partition which bluescreened; to be expected with different SATA controller though.

To add to what dave-boo said.

Make sure to use the new cooler than comes with the new CPU as it may have a different thermal profile (that will ensure you're using fresh thermal compound as well). It should use the existing retention bracket.

Reviewing the CPU support list: http://www.asus.com/Motherboards/AMD_AM2Plus/M3A78/#CPUS

It appears to support all AM3 CPUs when using BIOS version 0703 or above.

Good luck.

Thanks for the replies I had forgotten about the BIOS so will check and update first. I have a tube of thermal paste so can sort that too. Was mainly worried that Ubuntu might baulk but it sounds worth a try can always swap it back temporarily.

Thanks for the replies I had forgotten about the BIOS so will check and update first. I have a tube of thermal paste so can sort that too. Was mainly worried that Ubuntu might baulk but it sounds worth a try can always swap it back temporarily.

The only thing it would 'balk' at is the fact that you have an extra two cores; and by that I mean the compiler may not take that into account and you could be short changing yourself in certain circumstances. Luckily there's a nice easy way around this. Open a terminal and type in the following:

export CONCURRENCY_LEVEL=5

Technically you only need "4", but I use "5" because of tradition. It seems that someone did a study on a quad core and for his machine using "4" was fastest. Only thing I can suggest is to experiment and see what works best on your system.

Also of concern is updating to the latest kernel 2,6,38. It's much smoother on my hardware...