How many CPUs can M5 run?
• There is no inherent limit in M5 (other than simulation speed). In SE mode there are no obstacles to simulating as many CPUs as you want. However, in FS mode, the real-world Alpha platform we model (Tsunami) only supports up to 4 processors. To get around this limit, we defined and implemented a variant of the Tsunami platform (which we call BigTsunami) that can take up to 64 processors. Note that BigTsunami does not correspond to any real system. BigTsunami support is included in the standard M5 Alpha build, but booting with more than 4 CPUs requires modifications to the PAL code and kernel as well. Take a look at the Download page for our Linux patches and modified PAL code. Note that even with the BigTsunami changes, simulating 64 processors will be quite slow, and the Linux scheduler doesn’t seem particularly good at scheduling a large number of processors.
