
Glossary of Terms and Abbreviations
Glossary-11
TLB (translation lookaside buffer)
A cache that holds recently-used
page
table entries
.
Tenure
. The period of bus mastership. There can be separate address bus
tenures and data bus tenures. A tenure consists of three phases:
arbitration, transfer, termination.
Throughput
. The measure of the number of instructions that are processed
per clock cycle.
Transaction
. A complete exchange between two bus devices. A transaction
is minimally comprised of an address tenure; one or more data
tenures may be involved in the exchange. There are two kinds of
transactions: address/data and address-only.
Transfer termination
. Signal that refers to both signals that acknowledge the
transfer of individual beats (of both single-beat transfer and
individual beats of a burst transfer) and to signals that mark the end
of the tenure.
UISA (user instruction set architecture)
. The level of the architecture to
which user-level software should conform. The UISA defines the
base user-level instruction set, user-level registers, data types,
floating-point memory conventions and exception model as seen by
user programs, and the memory and programming models.
Unified cache
. Combined data and instruction cache.
User mode
. The unprivileged operating state of a processor used typically by
application software. In user mode, software can only access certain
control registers and can access only user memory space. No
privileged operations can be performed. Also referred to as problem
state.
VEA (virtual environment architecture)
. The level of the
architecture
that
describes the memory model for an environment in which multiple
devices can access memory, defines aspects of the cache model,
defines cache control instructions, and defines the time-base facility
from a user-level perspective.
Implementations
that conform to the
PowerPC VEA also adhere to the UISA, but may not necessarily
adhere to the OEA.
Virtual address
. An intermediate address used in the translation of an
effective address
to a physical address.
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