Technical data

CHALLENGE/Onyx Diagnostic Road Map 2-37
This problem also shows up as a system hang, where the system does not echo characters
on the serial console, not respond to network pings, and there is no disk or power meter
activity. The procedure in Section 2.5.5 can also help to pinpoint the bad MC3.
To deal with the clock jitter problem, there is an MC3 board with a KL-1 daughter card.
When this board is not available, there is a valuable workaround, which eliminates the
problem in many MC3 boards, called the “MC3 voltage reduction workaround.” The
workaround is described in the Challenge/Onyx Retrofit II Requirements document.
2.7.4 MC3 Error Latching
Sometimes the MC3 does not properly record errors. When an uncorrectable memory error
is detected during certain phases of data transfer, the MC3 may fail to record the error, or
incorrectly signal the error on a subsequent bus cycle.
Even if the error is not recorded, the MC3 still sends the data with bad parity. The CPU
board then records a Parity Error on data from d-chip. This is believed to the single
most frequent cause of an IP19 signaling the following message (with no other bits set):
+ IP19 in slot 3
+ CC in IP19 Slot 3, cpu 1
+ CC ERTOIP Register: 0x10
+ 4:Parity Error on Data from D-chip
The above symptom is probably caused by a failing MC3 or SIMM.
2.7.5 ECC Check Bit Single Bit Error
This problem appears similar to MC3 clock jitter. If a single bit error is encountered on the
ECC check bits, the MC3 will incorrectly signal a parity error on the EBUS. It may or may
not indicate My EBus Data Error, depending on the conditions listed in Section 2.7.4,
“MC3 Error Latching.”
+ MC3 in slot s
+ MA EBus Error register: 0x4
+ 2: My EBus Data Error
+ IP19 in slot s
+ CC in IP19 slot s, cpu c
+ CC ERTOPI Register: 0x10
+ 4:Parity Error on Data from D-chip
This problem is also indicative of a failing MC3 (or SIMMs).
2.7.6 SIMM failures
Uncommonly high error rates have been seen with type III SIMMs. A new test is now used
to catch marginal or failing SIMMs in manufacturing. If ECC errors or system hangs are
being seen in a system whose MC3 boards have been replaced, or are otherwise up to date,
the SIMMs should be replaced.