Are you sure? The last time I ran a Linux (YDL 3) on a dual 604e Mac, the second CPU was not active. Mac OS is required to get that second CPU active. This is in contrast to dual G4 processors which use a different architecture that Linux can enable.
A while back, Danamania said the same thing - that Debian, out of the box, works on dual 604e CPUs. Which seems strange because I thought that out-of-the-box support for PCI-class Macs was pretty much non-existant in ANY Linux distro. YDL, which is built specifically for PowerPC, doesn't even support those Macs anymore - since YDL 3, you have to figure out how to install it yourself.
Peace,
Drew