Hi @Josh_Guertler and welcome to the forum. OpenMC runs quite well multi-threaded, so I would recommend getting a CPU with as many cores as possible, even if it means that each core has a lower frequency. The performance is also generally pretty sensitive to the memory subsystem — the more data you can fit in cache the better, so all else being equal look for a CPU that has a large L3 cache. As for the total amount of RAM needed, that will entirely depend on the specifics of the problem you want to run so it’s hard to make a blanket recommendation there. Obviously the more RAM you have, the larger a problem (in terms of number of tallies, etc.) you’ll be able to run.