Fujitsu Fujitsu SPARC64 V manual Error in U2 Unified Level 2 Cache Tag

Models: Fujitsu SPARC64 V

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When a parity error is detected in a D1 cache tag entry or in a D1 cache tag copy entry, hardware automatically corrects the error by copying the correct tag entry from the other copy of the tag entry. If the error can be corrected in this way, program execution is unaffected.

Similarly, when a parity error is detected in an I1 cache tag entry or in a I1 cache tag copy entry, hardware automatically corrects the error by copying the correct tag entry from the other copy of the tag entry. If the error can be corrected in this way, program execution is unaffected.

When the error in the level-1 cache tag or tag copy is not corrected by the tag copying operation, the tag copying is repeated. If the error is permanent, a watchdog timeout or a FATAL error is then detected.

Error in U2 (Unified Level 2) Cache Tag

The U2 cache tag is protected by double-bit error detection and single-bit error correction ECC code.

When a correctable error is detected in a U2 cache tag, hardware automatically corrects the error by rewriting the corrected data into the U2 cache tag entry. The error is not reported to software.

When an uncorrectable error is detected in a U2 cache tag, one of following actions is taken, depending on the setting of OPSR (internal mode register set by the JTAG command):

1.A fatal error is detected and the CPU enters the CPU fatal error state.

2.The U2 cache tag uncorrectable error is treated as follows; however, in some cases, the fatal error is still detected.

a.When ASI_ERROR_CONTROL.WEAK_ED = 0:

The AUG_SDC is recognized during U2 cache tag error detection.

If ASI_ERROR_CONTROL.UGE_HANDLER = 0, the AUG_SDC immediately generates an async_data_error trap with ASI_UGESR.AUG_SDC = 1.

Otherwise:, if ASI_ERROR_CONTROL.UGE_HANDLER = 1, the AUG_SDC remains pending in hardware. At the point when

ASI_ERROR_CONTROL.UGE_HANDLER is set to 0, an async_data_error exception is generated, with ASI_UGESR.AUG_SDC = 1.

b.When ASI_ERROR_CONTROL.WEAK_ED = 1:

Hardware ignores the U2 cache tag error if possible. However, the AUG_SDC or fatal error may still be detected.

Release 1.0, 1 July 2002

F. Chapter P Error Handling 189

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Fujitsu Fujitsu SPARC64 V manual Error in U2 Unified Level 2 Cache Tag