So I've got a question for the list, hardware oriented. And yes, I know
that strictly speaking, what we're talking about here isn't "Qbus
memory." I'm talking about memory boards for modern (?) Q-Bus machines,
with the memory interconnect jumper.

What memory modules are compatible with what processors?

In other words, can I take memory from a KA650 and attach it to a KA660?
I know that the KA630 and KA640/65x style memory boards are different,
but are the KA650 memory boards compatible with 4000-series CPUs?

Also, perhaps important in the near future, if nobody outbids me - can
memory in a 4000/200 be used by a 4000/500?