Due to the generosity of the administrator team from TuxFamily.org, I can now run rebuildd on octave, their (spare) HP NetServer LXr 8500 (8xPIII 500 MHz / 2 GB RAM). Which is quite faster that the P4 1.4 GHz I used for my first tests.

I can now run 24 builds in parallel. :-) HP Netserver TF