Intel SL7PG - Xeon 3.4 GHz/800MHz/1MB Cache CPU Processor Specification page 21

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.
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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.
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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.
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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.
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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.
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A different mechanism than the rest of the register writes the MCA Error Code field of the
IA32_MC0_STATUS 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.
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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.
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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
occurs and the address is not available because the linear to physical address translation is not
complete or an internal resource conflict has occurred, the Address Valid bit is incorrectly set.
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The processor may hang when an instruction code fetch receives a hard failure response from
the front side bus. This occurs because the bus control logic does not return data to the core,
leaving the processor empty. IA32_MC0_STATUS MSR does indicate that a hard fail
response occurred.
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The processor may hang when the following events occur and the machine check exception is
enabled, CR4.MCE=1. A processor that has it's STPCLK# pin asserted will internally enter
the Stop Grant State and finally issue a Stop Grant Acknowledge special cycle to the bus. If an
uncorrectable error is generated during the Stop Grant process it is possible for the Stop Grant
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64-bit Intel Xeon Processor with 800 MHz System Bus
(1 MB and 2 MB L2 Cache Versions) Specification Update
Errata
21