The most aged system I have Solus installed is K8-sse3.
In a generic term it's a -march=nocona -mtune=generic -msahf
It's still a very capable machine, my main home station in fact. Handles two 4k monitors without problem.
Almost core2 minus -mssse3
By the way, no one actually owns pure x86_64 anymore, i believe. The actual baseline in the wild is some K8-sse3 successor, i.e. core2 minus -mssse3
. I can only speculate that some 90nm Nocona's are still alive but have not seen them myself. "K8-sse3" successors - seen plenty of them with my own eyes.
-march=k8-sse3 -mno-3dnow -mtune=generic
- in my personal research that includes everything that is not a dead silicon.