localhost ~ # emerge --ask --verbose =x11-drivers/ati-drivers-8.42.3-r10

These are the packages that would be merged, in order:

Calculating dependencies... done!
[ebuild     U ] x11-drivers/ati-drivers-8.42.3-r10 [8.40.4-r11] USE="acpi distribution (-multilib)" 49,285 kB [1]

Total: 1 package (1 upgrade), Size of downloads: 49,285 kB
Portage tree and overlays:
 [0] /usr/portage
 [1] /usr/portage/local/layman/sabayon

Would you like to merge these packages? [Yes/No]