Ev68 Single-Bit Errors; Syndrome To Data Check Bits Table - Compaq AlphaServer ES45 Service Manual

E.3

EV68 Single-Bit Errors

The procedure for detection down to the set of DIMMs for a single-bit
error is very similar to the procedure described in the previous
sections. However, you cannot isolate down to a specific data or check
bit.
The 21264 (EV68) chip detects and reports a C_ADDR<42:6> failing address
that is accurate to the cache block (64 bytes). The syndrome registers (Table E–
6) detect data syndrome information, providing isolation down to the low or high
quadword of the target octaword that the fault has been detected within. Each
of the syndrome registers is able to report 64 data bits (the quadword) and 8
check bits (memory data bus ECC bits).
Table E–6 shows the syndrome hexadecimal to physical data or check bit
decoding. For example, if you have an EV68 single-bit C_Syndrome_0 hexadeci-
mal error value equal to 23, the second column indicates the decoded physical
data or check bit for this encoding. Use these physical data bits in conjunction
with the previously described isolation procedure to isolate the failing DIMMs.
Table E–6 Syndrome to Data Check Bits Table
Syndrome C_Syndrome 0
CE Data Bit 0 or 128
CB Data Bit 1 or 129
D3 Data Bit 2 or 130
D5 Data Bit 3 or 131
D6 Data Bit 4 or 132
D9 Data Bit 5 or 133
DA Data Bit 6 or 134
DC Data Bit 7 or 135
23 Data Bit 8 or 136
25 Data Bit 9 or 137
26 Data Bit 10 or 138
29 Data Bit 11 or 139
2A Data Bit 12 or 140
2C Data Bit 13 or 141
C_Syndrome 1
Data Bit 64 or 192
Data Bit 65 or 193
Data Bit 66 or 194
Data Bit 67 or 195
Data Bit 68 or 196
Data Bit 69 or 197
Data Bit 70 or 198
Data Bit 71 or 199
Data Bit 72 or 200
Data Bit 73 or 201
Data Bit 74 or 202
Data Bit 75 or 203
Data Bit 76 or 204
Data Bit 77 or 205
Isolating Failing DIMMs E-19