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21264/EV68A Hardware Reference Manual
Error Detection and Error Handling 8–9
Bcache Data Single-Bit Correctable ECC Error on a Probe
8.11 Bcache Data Single-Bit Correctable ECC Error on a Probe
The probed processor extracts the block from its Bcache, signaling a corrected read
data (CRD) error and latching error information. The single-bit ECC detected error data
is not corrected by the probed processor, but is forwarded to the requesting processor.
The requesting processor then detects a related system fill error as a result of this sys-
tem probe transaction.
• No hardware correction is performed.
• C_STAT[PROBE_BC_ERR] is set.
• C_ADDR contains bit [42:6] of the Bcache address of the block that contains the
error.
• C_SYNDROME_0[7:0] and C_SYNDROME_1[7:0] contain the syndrome of
quadword 0 and 1, respectively, of the octaword subblock that contains the error.
• A CRD error interrupt is posted, when enabled.
• The PALcode on the probed processor may choose to scrub the error, though it will
probably be scrubbed by the requesting processor.
8.12 Double-Bit Fill Errors
Double-bit errors for fills are detected, but not corrected, in the 21264/EV68A. The fol-
lowing events may cause a double-bit fill error:
• Icache fill from Bcache
• Dcache fill from Bcache
• Icache fill from memory
• Dcache fill from memory
If an error is detected, the following actions are taken:
• C_STAT is set to one of the following:
ISTREAM_BC_DBL (Icache fill from Bcache)
DSTEAM_BC_DBL (Dcache fill from Bcache)
ISTREAM_MEM_DBL (Icache fill from memory)
DSTREAM_MEM_DBL (Dcache fill from memory)
• C_ADDR contains bits [42:6] of the system memory fill address of the block that
contains the error.
• When enabled, a machine check (MCHK) is posted. The MCHK is taken when not
in PALmode.
• A double-bit fill error from memory, marked by the data's corresponding ECC,
when written to cache, also writes the corresponding ECC to cache. Any consumer
of that error (such as another CPU) also consumes the corresponding ECC value.
Note: C_ADDR may be inaccurate in heavy traffic conditions. C_STAT is accu-
rate.