
Glossary-8
PowerPC Microprocessor Family: The Bus Interface for 32-Bit Microprocessors
Out-of-order
. An aspect of an operation that allows it to be performed ahead
of one that may have preceded it in the sequential model, for
example, speculative operations. An operation is said to be
performed out-of-order if, at the time that it is performed, it is not
known to be required by the sequential execution model.
See
In-order.
Overflow
. An error condition that occurs during arithmetic operations when
the result cannot be stored accurately in the destination register(s).
For example, if two 32-bit numbers are multiplied, the result may not
be representable in 32 bits.
Packet
. A term used with respect to direct-store operations.
Page
. A region in memory. The OEA defines a page as a 4-Kbyte area of
memory, aligned on a 4-Kbyte boundary.
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.
Park
. The act of allowing a bus master to maintain mastership of the bus
without having to arbitrate.
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
. The pipeline can be stopped so the instructions that
preceded the faulting instruction can complete, and subsequent
instructions can be executed following the execution of the exception
handler. The system is precise unless one of the imprecise modes for
invoking the floating-point enabled exception is in effect.
Physical memory
. The actual memory that can be accessed through the
system’s memory bus.
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