Sun Microelectronics
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UltraSPARC Basics
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1.1 Overview
UltraSPARC is a high-performance, highly integrated superscalar processor im-
plementing the 64-bit SPARC-V9 RISC architecture. UltraSPARC is capable of sus-
taining the execution of up to four instructions per cycle, even in the presence of
conditional branches and cache misses. This is due mainly to the asynchronous
aspect of the units feeding instructions and data to the rest of the pipeline. In-
structions predicted to be executed are issued in program order to multiple func-
tional units, execute in parallel and, for added parallelism, can complete out-of-
order. In order to further increase the number of instructions executed per cycle
(IPC), instructions from two basic blocks (that is, instructions before and after a
conditional branch) can be issued in the same group.
UltraSPARC is a full implementation of the 64-bit SPARC-V9 architecture. It sup-
ports a 44-bit virtual address space and a 41-bit physical address space. The core
instruction set has been extended to include graphics instructions that provide
the most common operations related to two-dimensional image processing, two-
and three-dimensional graphics and image compression algorithms, and parallel
operations on pixel data with 8- and 16-bit components. Support for high band-
width bcopy is also provided through block load and block store instructions.
1.2 Design Philosophy
The execution time of an application is the product of three factors: the number of
instructions generated by the compiler, the average number of cycles required per
instruction, and the cycle time of the processor. The architecture and implementa-
tion of UltraSPARC, coupled with new compiler techniques, makes it possible to
reduce each component while not deteriorating the other two.
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