
MOTOROLA
Glossary of Terms and Abbreviations
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Glossary-9
Normalization.
A process by which a floating-point value is manipulated
such that it can be represented in the format for the appropriate
precision (single- or double-precision). For a floating-point value to
be representable in the single- or double-precision format, the
leading implied bit must be a 1.
O
OEA (operating environment architecture).
The level of the architecture
that
describes
PowerPC
supervisor-level registers, synchronization requirements, and the
exception model. It also defines the time-base feature from a
supervisor-level perspective. Implementations that conform to the
PowerPC OEA also conform to the PowerPC UISA and VEA.
memory
management
model,
Optional.
A feature, such as an instruction, a register, or an exception, that
is defined by the PowerPC architecture but not required to be
implemented.
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
.
Out-of-order execution.
A technique that allows instructions to be issued
and completed in an order that differs from their sequence in the
instruction stream.
Overflow.
An 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. Since the 32-bit registers of the G2 cannot
represent this sum, an overflow condition occurs.
P
Page.
A region in memory. The OEA defines a page as a 4-Kbyte area of
memory, aligned on a 4-Kbyte boundary.
Page access history bits.
The
changed
and
referenced
bits in the PTE keep
track of the access history within the page. The referenced bit is set
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
.
F
Freescale Semiconductor, Inc.
n
.