Yeah, I have a few with a lot of cores now I use for various things, but I have a machine with 8x Xeon physical CPUs that's quite good for an entry level high compute.  Later I'd like to get into the AMD EPYC CPUs but I don't think I'll be able to do that for a year or so yet.  Each CPU is around $5k I think, I could go slowly with boards in a rack mount that can handle 2x EPYC 7000-series 32-core CPUs and start collecting them.

There are good ways of designing coins that are CPU minable only by having highly serial PoW algorithms, which are amazingly ASIC and GPU resistant, also having high and fast memory requirements where parallelism isn't feasible.  The problem with that is that it can't be too hard otherwise the average person at home can't mine and get any coins.  If they do, those with big rigs will get pretty much all of them.  That's why I like the idea that sprang out of LuckyCoin, the predecessor to DogeCoin (I think...)

So it essentially becomes a lottery coin.  It can be mined on your mobile phone as well.  The PoW rewards according to what random type of selection you make in advance (e.g. 8 hex chars in sequence of the next block hash).  The first to submit with the earliest timestamp wins the block reward.  For a long in-sequence PoW the block reward could be 100 coins; for any 5 out of 10 maybe 1 coin, and a lot of people could share in that.  It would have to be a big or infinite supply coin though, perhaps.  The hard part is how to prevent knowing what the next block hash (double SHA512 of the block) is going to be.  Mobile phone mining could become popular by having an app that submits your hex chars to the network every 5 minutes or so, timestamped and eventually the network will reject submissions and the earliest timestamp with winning "lotto numbers" of the upcoming block hash takes the coins, which could be a lot of people in the case of high probability finds.  Faking the timestamp could be attempted although full nodes would check them out to ensure they seem reasonable, within some condition like timestamp T must be 2 minutes ago < T < 2 minutes before next expected block hash found.  The actual block hashes could only be submitted very quickly within the expected time interval containing the block header and transactions, so there's that option for other miners with electricity to contribute to the network; those finding the SHA512d(block) would always claim an N coin reward.  They would be excluded from submitting lottery mining tickets, though.  This coin would probably still eat a little too much power but otherwise be a lot eco-friendly than coins that consume enormous amounts of power to keep running.

Armagerd it's almost 6am and I'm rambling already.