Occasional network lockups have been noted when the PIT has a higher
interrupt request level than the CPM. The SCC1 bit in the CISR is set
even though the SCC1 interrupt handler is not active. This blocks
interrupts from SCC1 (and all other CPM sources) and locks up the
system. It has not been determined whether the error is within the
68360 or in the RTEMS interrupt support assembler code. The solution,
for now, is to set both PIT and CPM interrupt request levels to the same
value (4).