Intel Xeon Processor Specification Update

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

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