Could you put a few thousand of these on a PCB and have a super duper tiny compute cluster?
Yes, but also why would you? at 24MHz, you would be better off paying 100x the price ($25) for a 2.4GHz chip (easily doable). Something like a Raspbery Pi Zero 2 W already comes pretty close to that and without the penalty of memory communication/bandwidth.
I'm reminded of TIS-100, a game where you program a cluster of tiny, parallel CPUs using a custom assembly language. It's painful to get basic stuff done, but you can do some amazing things with some effort.
https://hackaday.com/2025/07/07/160-core-risc-v-board-is-the...
I could only imagine the bringup fun for thousands of them. :P
No.
Yes, if you want all the drawbacks of distributed computing with none of the advantages: You'd probably be stuck with something UART based as interconnect, Every core is gonna have way too little RAM to do anything useful, you are missing like half the instruction set (floating point operations in software), and power draw at 4mW minimum per core adds up quickly to something that an efficient laptop-CPU would use.
On top of all this, latency for anything is gonna be abysmal because the cores are so slow...
I honestly don't see an application where this is even close to desirable.
Would be fun, tough, to have a 10-stack of PCBs with 10 by 10 CPUs each for a thousand cores (=> ~4W power @1.8V).