When booting Fiasco/L4Re on my test machine (16G RAM, quad-core i7), I get the following error message, unless I have all CPUs and HyperThreading active:
L4 Bootstrapper
Build: #2 Mon Jun 3 14:15:47 CEST 2013, x86-32, 4.8.0
Limiting 'RAM' region [100000000, 43e5fffff] {33e600000} to [100000000, 10ea803ff] { ea80400} due to 3024 MB limit
Bootstrap: add_nolimitcheck: Region overflow
As soon as I deactivate CPUs in the BIOS or deactivate HT, it fails.
Increasing the buffer __ram[8] to, e.g., __ram[16] in bootstrap/server/src/startup.cc:L67 does the trick.