If a monothreaded eix-update was run immediately after a polythreaded eix, there's a high chance that a lot of the data from /usr/portage was in the disk cache. I'd like to see the results of running the test back-to-back multiple times (eix, cached eix, monothreaded eix, cached monothreaded eix), which might eliminate the caching delta.
Actually no, I repeated it several times in read only after a cold boot start on the 2 sysreccd kernel and altkernel.
The limiting factor is CPU bound.
Note: I have a quite fast SSD at around 500MB/s so the results may differ on other machines.
