NXP Semiconductors Lite5200B, Руководство пользователя, Страница: 122 / 138

LITE5200B User’s Manual, Rev. 2
Glossary-4 Freescale Semiconductor
Exclusive state. MEI state (E) in which only one caching device contains data that is also
in system memory.
Execution synchronization. A mechanism by which all instructions in execution are
architecturally complete before beginning execution (appearing to begin
execution) of the next instruction. Similar to context synchronization but doesn't
force the contents of the instruction buffers to be deleted and refetched.
Exponent. In the binary representation of a floating-point number, the exponent is the
component that normally signifies the integer power to which the value two is
raised in determining the value of the represented number. See also Biased
exponent .
F
Feed-forwarding. A 603e feature that reduces the number of clock cycles that an
execution unit must wait to use a register. When the source register of the current
instruction is the same as the destination register of the previous instruction, the
result of the previous instruction is routed to the current instruction at the same
time that it is written to the register file. With feed-forwarding, the destination bus
is gated to the waiting execution unit over the appropriate source bus, saving the
cycles which would be used for the write and read.
Fetch. Retrieving instructions from either the cache or main memory and placing them
into the instruction queue.
Floating-point register (FPR). Any of the 32 registers in the floating-point register file.
These registers provide the source operands and destination results for
floating-point instructions. Load instructions move data from memory to FPRs
and store instructions move data from FPRs to memory. The FPRs are 64 bits wide
and store floating-point values in double-precision format.
Floating-point unit. The functional unit in the 603e processor responsible for executing
all floating-point instructions.
Flush. An operation that causes a cache block to be invalidated and the data, if modified,
to be written to memory.
Fraction. In the binary representation of a floating-point number, the field of the
significand that lies to the right of its implied binary point.
G
General-purpose register (GPR). Any of the 32 registers in the general-purpose register
file. These registers provide the source operands and destination results for all
integer data manipulation instructions. Integer load instructions move data from
memory to GPRs and store instructions move data from GPRs to memory.
Guarded. The guarded attribute pertains to out-of-order execution. When a page is
designated as guarded, instructions and data cannot be accessed out-of-order.
H
Harvard architecture. An architectural model featuring separate caches and other
memory management resources for instructions and data.