It's not a Computer, but I know for a fact that an
HP5MP Laserjet will not
work with 60ns RAM, it wants 70ns RAM (company I bought the RAM from sent
60ns by mistake). It just plain wouldn't recognize the RAM.
I suspect some other incompatibility was the problem, since plenty of 70 ns
will actually run at 60 ns. I never heard of a memory process test to be
sure memory would not run at a slightly higher speed under at least some
conditions.