Intel
®
Xeon
®
Processor Specification Update
33
Errata
Implication:
When this erratum occurs, FPU Operand (Data) Pointer (FDP) may become corrupted.
Workaround:
This erratum will not occur with floating point exceptions masked. If FP exceptions are unmasked,
then performance counting of x87 loads should be disabled.
Status:
For the steppings affected, see the
Summary Table of Changes
.
P17
Simultaneous code breakpoint and uncorrectable error results in processor
hang
Problem:
If an instruction fetch results in an uncorrectable error and there is also a debug breakpoint at this
address, the processor will hang and the uncorrectable error will not be logged in the machine
check registers.
Implication:
When this erratum occurs the processor will hang.
Workaround:
None at this time.
Status:
For the steppings affected, see the
Summary Table of Changes
.
P18
Software controlled clock modulation using a 12.5% or 25% duty cycle may
cause the processor to hang
Problem:
Per the ACPI 1.0b specification, processor clock modulation may be controlled via a processor
register (IA32_THERM_CONTROL). The On-Demand Clock Modulation Duty Cycle is
controlled by bits 3:1. If these bits are set to a duty cycle of 12.5% or 25%, the processor may hang
while attempting to execute a FP instruction. In this failure, the last instruction pointer (LIP) is
pointing to a FP instruction whose instruction bytes are in UC space and which takes an exception
16 (FP error exception). The processor stalls trying to fetch the bytes of the faulting FP instruction
and those following it. This processor hang is caused by interactions between the thermal control
circuit and FP event handler.
Implication:
When the clock modulation is set to 12.5% or 25% duty cycle, the processor will go into a sleep
state from which it fails to return.
Workaround:
Use a duty cycle other than 12.5% or 25%.
Status:
For the steppings affected, see the
Summary Table of Changes
.
P19
RFO with ECC error may result in incorrect data
Problem:
This erratum occurs as the result of the following conditions:
•
A Request for Ownership (RFO) generates a correctable error.
•
In the process of correcting the error, a locked RFO (LRFO) is issued that uses the same
internal buffer as the previous RFO.
•
Another processor issues a snoop to the same address as the LRFO.
An internal boundary condition exists which may prevent the LRFO from completing correctly
causing the snoop to receive incorrect data. Intel has not been able to reproduce this erratum with
commercial software.
Implication:
When this erratum occurs, data corruption may result.
Workaround:
None at this time.
Status:
For the steppings affected, see the
Summary Table of Changes
.
P20
Speculative page-fault may cause livelock
Problem:
If the processor detects a page-fault, which is corrected before the operating system page-fault
handler can be called (e.g., a second processor or DMA activity modifies the page tables and the
