30
Intel
®
Xeon
®
Processor Specification Update
Errata
the L1 cache, the cache controller logic may write the physical address from a subsequent load
or store operation into the IA32_MC1_ADDR register.
•
When an error exists in the tag field of a cache line such that a read for ownership (RFO)
issued by the processor hits multiple tag fields in the L2 cache (the correct tag and the tag with
the error) and the accessed data also has a correctable error, the processor will correctly log the
multiple tag match error but will hang when attempting to execute the machine check
exception handler.
•
If a memory access receives a machine check error on both 64 byte halves of a 128-byte L2
cache sector, the IA32_MC0_STATUS register records this event as multiple errors, i.e., the
valid error bit and the overflow error bit are both set indicating that a machine check error
occurred while the results of a previous error were in the error-reporting bank. The
IA32_MC1_STATUS register should also record this event as multiple errors but instead
records this event as only one correctable error.
•
The overflow bit should be set to indicate when more than one error has occurred. The
overflow bit being set indicates that more than one error has occurred. Because of this erratum,
if any further errors occur, the MCA overflow bit will not be updated, thereby incorrectly
indicating only one error has been received.
•
If an I/O instruction (IN, INS, REP INS, OUT, OUTS, or REP OUTS) is being executed, and if
the data for this instruction becomes corrupted, the processor will signal a MCE. If the
instruction is directed at a device that is powered down, the processor may also receive an
assertion of SMI#. Since MCEs have higher priority, the processor will call the MCE handler,
and the SMI# assertion will remain pending. However, while attempting to execute the first
instruction of the MCE handler, the SMI# will be recognized and the processor will attempt to
execute the SMM handler. If the SMM handler is successfully completed, it will attempt to
restart the I/O instruction, but will not have the correct machine state due to the call to the
MCE handler. This can lead to failure of the restart and shutdown of the processor.
•
If PWRGOOD is deasserted during a RESET# assertion causing internal glitches, the MCA
registers may latch invalid information.
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If RESET# is asserted, then deasserted, and reasserted, before the processor has cleared the
MCA registers, then the information in the MCA registers may not be reliable, regardless of
the state or state transitions of PWRGOOD.
•
If MCERR# is asserted by one processor and observed by another processor, the observing
processor does not log the assertion of MCERR#. The MCE handler called upon assertion of
MCERR# will not have any way to determine the cause of the MCE.
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The Overflow Error bit (bit 62) in the IA32_MC0_STATUS register indicates, when set, that a
machine check error occurred while the results of a previous error were still in the error
reporting bank (i.e. The Valid bit was set when the new error occurred). If an uncorrectable
error is logged in the error-reporting bank and another error occurs, the overflow bit will not be
set.
•
The MCA Error Code field of the IA32_MC0_STATUS register gets written by a different
mechanism than the rest of the register. For uncorrectable errors, the other fields in the
IA32_MC0_STATUS register are only updated by the first error. Any further errors that are
detected will update the MCA Error Code field without updating the rest of the register,
thereby leaving the IA32_MC0_STATUS register with stale information.
•
When a speculative load operation hits the L2 cache and receives a correctable error, the
IA32_MC1_Status Register may be updated with incorrect information. The
IA32_MC1_Status Register should not be updated for speculative loads.
•
The processor should only log the address for L1 parity errors in the IA32_MC1_Status
register if a valid address is available. If a valid address is not available, the Address Valid bit
in the IA32_MC1_Status register should not be set. In instances where an L1 parity error
