Compaq EV68A Bcache Data Single-Bit Correctable ECC Error on a Probe, Double-Bit Fill Errors

Models: EV68A

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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.

8.12Double-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.

21264/EV68A Hardware Reference Manual

Error Detection and Error Handling 8–9

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Compaq EV68A specifications Bcache Data Single-Bit Correctable ECC Error on a Probe, Double-Bit Fill Errors