Specification Update

R
Mobile Intel® Celeron® Processor Specification Update 39
a corresponding bus transaction, causing the processor to hang (livelock). The exact circumstances are
complex, and include the relative timing of internal processor functions with the snoop request from a
bus agent.
Implication: This erratum may occur on a system with any number of processors. However, the probability of
occurrence increases with the number of processors. If this erratum does occur, the system will hang
with DBSY# asserted. At this point, the system requires a hard reset.
Workaround: It is possible for BIOS code to contain a workaround for this erratum.
Status: For the steppings affected see the Summary of Changes at the beginning of this section.
M39.
IFU/DCU Deadlock May Cause System Hang
Problem: An internal deadlock situation may occur in systems with multiple bus agents, with a failure signature
such that a processor either asserts DBSY# without issuing the corresponding data, or fails to respond to
a snoop request from another bus agent. Should this erratum occur, the affected processor ceases code
execution and the system will hang.
The specific circumstances surrounding the occurrence of this erratum are:
1. A locked operation to the Data Cache Unit (DCU) is in process.
2. A snoop occurs, but cannot complete due to the ongoing locked operation.
3. The presence of the snoop prevents pending Instruction Fetch Unit (IFU) requests from completing.
4. The IFU requests are periodically restarted.
The continued IFU restart attempts create additional DCU snoops, which prevent the in-process locked
operation from completing, keeping the DCU locked.
Implication: The system may hang.
Workaround: It is possible for BIOS code to contain a workaround for this erratum.
Status: For the steppings affected see the Summary of Changes at the beginning of this section.
M40.
WBINVD May Lock Write Out Buffer
Problem: If a processor is performing a WBINVD operation on a modified line, that line is stored in the
processor's Write Out Buffer (WOB) until it is written to main memory. If another bus agent (such as a
processor or PCI device) in the system generates a snoop that results in a hit to a modified line that is in
the processor's WOB, that line could become permanently locked in the WOB. In addition to being
locked in the WOB, the processor will not respond to the initial or subsequent snoop requests to this line,
and the line in the WOB is never written to memory.
Implication: In the event of this erratum, coherency may be lost, which may result in a system lockup or system
instability.
Workaround: None identified
Status: For the steppings affected see the Summary of Changes at the beginning of this section.