Specification Update

MOBILE INTEL

CELERON

PROCESSOR at 466 MHz, 433 MHz, 400 MHz,

366 MHz, 333 MHz, 300 MHz, 266 MHz SPECIFICATION UPDATE

H55. Selector for The LTR/LLDT Register May Get Corrupted

Problem: The internal selector portion of the respective register (TR, LDTR) may get corrupted if, during a

small window of LTR or LLDT system instruction execution, the following sequence of events occur:

1. Speculative write to a segment register that might follow the LTR or LLDT instruction

2. The read segment descriptor of LTR/LLDT operation spans a page (4 Kbytes) boundary; or causes a

page fault

Implication: Incorrect selector for LTR, LLDT instruction could be used after a task switch.

Workaround: Software can insert a serializing instruction between the LTR or LLDT instruction and the

segment register write.

Status: For the steppings affected see the Summary of Changes at the beginning of this section.

H56. INIT Does Not Clear Global Entries in The TLB

Problem: INIT may not flush a TLB entry when:

1. The processor is in protected mode with paging enabled and the page global enable flag is set (PGE bit of

CR4 register)

2. G bit for the page table entry is set

3. TLB entry is present in TLB when INIT occurs

Implication: Software may encounter unexpected page fault or incorrect address translation due to a TLB entry

erroneously left in TLB after INIT.

Workaround: Write to CR3, CR4 or CR0 registers before writing to memory early in BIOS code to clear all the

global entries from TLB.

Status: For the steppings affected see the Summary of Changes at the beginning of this section.

H57. VM Bit Will Be Cleared on a Double Fault Handler

Problem: Following a task switch to a Double Fault Handler that was initiated while the processor was in

virtual-8086 (VM86) mode, the VM bit will be incorrectly cleared in EFLAGS.

Implication: When the OS recovers from the double fault handler, the processor will no longer be in VM86

mode.

Workaround: None identified

Status: For the steppings affected see the Summary of Changes at the beginning of this section.