You don't need more.

you need at least a PSU, motherboard and some RAM

Which workloads were these bad in due to the gimped design where multiple cores shared an FPU (or whatever it was)?

if you want to use old shit stick to overclockable xeons, they can still mog some modern processors
FX cpus are worse than the previous gen's phenoms btw

>>105868824
>Which workloads were these bad in
My guess, single-threaded and desktop performance. With, potentially, the exception of a BSD OS running a certain flag.

>>105868824
Any workload that uses more than half the cores will suffer to a degree. They don't just share FPUs but instruction decoders. It's essentially hardware SMT