Glossary of Terms and Abbreviations
Glossary-9
by the MMU whenever the page is accessed for a read or write
operation. The changed bit is set when the page is stored into. See
Changed bit and Referenced bit.
Page fault
. A page fault is a condition that occurs when the processor
attempts to access a memory location that does not reside within a
page
not currently resident in
physical memory
. On PowerPC
processors, a page fault exception condition occurs when a
matching, valid
page table entry
(PTE[V] = 1) cannot be located.
Page table
. A table in memory is comprised of
page table entries
, or PTEs.
It is further organized into eight PTEs per PTEG (page table entry
group). The number of PTEGs in the page table depends on the size
of the page table (as speciTed in the SDR1 register).
Page table entry (PTE)
. Data structures containing information used to
translate
effective address
to physical address on a 4-Kbyte page
basis. A PTE consists of 8 bytes of information in a 32-bit processor
and 16 bytes of information in a 64-bit processor.
Physical memory
. The actual memory that can be accessed through the
systems memory bus.
Pipelining
. A technique that breaks operations, such as instruction
processing or bus transactions, into smaller distinct stages or tenures
(respectively) so that a subsequent operation can begin before the
previous one has completed.
Precise exceptions
. A category of exception for which the pipeline can be
stopped so instructions that preceded the faulting instruction can
complete, and subsequent instructions can be ushed and
redispatched after exception handling has completed.
See
Imprecise
exceptions.
Primary opcode
. The most-signiTcant 6 bits (bits 0D5) of the instruction
encoding that identiTes the type of instruction.
Program order
. The order of instructions in an executing program. More
speciTcally, this term is used to refer to the original order in which
program instructions are fetched into the instruction queue from the
cache
Protection boundary
. A boundary between
protection domains
.
Protection domain
. A protection domain is a segment, a virtual page, a BAT
area, or a range of unmapped effective addresses. It is deTned only
when the appropriate relocate bit in the MSR (IR or DR) is 1.