I thought it was just the PowerPC one (which had a different, Mach-based kernel), but it turns out¹ that it has had some sort of SMP support since 2.11 in 1993.

I thought it was just the PowerPC one (which had a different, Mach-based kernel), but it turns out¹ that it has had some sort of SMP support since 2.11 in 1993. 1. http://www.edm2.com/0509/smp2.html http://www.edm2.com/0509/smp2.html