Intel SL79K Specification Update - Page 32

Errata R • When one-half of a 64-byte instruction fetch from the L2 cache has an uncorrectable error and the other 32-byte half of the same fetch from the L2 cache has a correctable error, the processor will attempt to correct the correctable error but cannot proceed due to the uncorrectable error. When this occurs the processor will hang. • When an L1 cache parity error occurs, the cache controller logic should write the physical address of the data memory location that produced that error into the IA32_MC1_ADDR REGISTER (MC1_ADDR). In some instances of a parity error on a load operation that hits 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 request 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 Machine Check Exception (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 de-asserted during a RESET# assertion causing internal glitches, the MCA registers may latch invalid information. • If RESET# is asserted, then de-asserted, 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 Machine Check Exception (MCE) handler called upon assertion of MCERR# will not have any way to determine the cause of the MCE. 32 Intel® Pentium® 4 Processor on 90 nm Process Specification Update