When the Versatile Interface Processor (VIP) tries to write to an invalid address in the packet memory (MEMD), the Route Switch Processor (RSP) places a Negative Acknowledgement (NACK) message on the CyBus for that slot. This is usually a software problem, but can also be a hardware problem. In this example, the VIP writes four bytes to an invalid address, so the RSP places a NACK on the CyBus for that slot:
If a parity error is indicated, and the card recovers, a primary cache or Processor Memory Parity Error (PMPE) may be a transient error. If this is the first instance of a PMPE, you can usually ignore it. However if the same VIP experiences a second, or subsequent PMPE, you should replace the VIP. Replacing the DRAM itself can also resolve the issue.
When a NACK appears on all slots, as shown in this example, it is a hardware error. In this case, the arbiter is faulty and the card cage must be replaced:
Jan 1 23:55:21: %FEIP2-1-MSG: slot0 Nevada Error Interrupt Register =0x1
Jan 1 23:55:21: %FEIP2-1-MSG: slot0 CYASIC Error Interrupt register0x20000001
Jan 1 23:55:21: %FEIP2-1-MSG: slot0 NACK present on CyBus access
Jan 1 23:55:21: %FEIP2-1-MSG: slot0 CYASIC Other Interrupt register 0x0
Jan 1 23:55:21: %FEIP2-1-MSG: slot0 CYBUS Error register 0x8001A00,