Note 3: System Bus Read Parity Error; Note 4: Backup Cache Uncorrectable Error - DEC 4000 AXP Service Manual

Examine the commander's command trap register to identify the respective
responder.
• _WD_NOACK errors with the responder reporting _WD_PAR errors could
indicate a failure with either device.
• _WD_PAR errors without respective _WD_NOACK would require two failures
to occur:
1. Bad data received by responder
2. A valid response was received when one should not have been sent.
The failing module could be either partner in the transfer.

4.4.3 Note 3: System Bus Read Parity Error

Synopsis:
System bus read-data failures are reported only by the bus commander.
• By commander: _RD_PAR error—Read-data parity error.
The bus commander (device reporting _RD_PAR) detected a parity error on
data received from the system bus.
Analysis:
Only the bus commander checks write-data parity on bus reads.
• The failure could be caused by either the bus commander or responder. The
failing data's address is captured in the commander's bus trap register.
• A system bus read parity error can result as a side effect of a command/address
NOACK.

4.4.4 Note 4: Backup Cache Uncorrectable Error

Synopsis:
Data from the backup cache is either delivered to the DECchip 21064
microprocessor or the system bus interface chip is corrupted.
Analysis:
4–14 Error Log Analysis
Note