the market of wireless handheld devices growing at lighting speed, all
devices are in need of embedding more complexity into the devices.
More complexity will drive the need for more power which today limits
the processor used in the devices. The use of RISC processors over CISC
processors in embedded Wireless systems today is wide spread and seems
to be the trend of the future. Special RISC processors are giving more
value with there power saving features, giving the much needed help in
developing Wireless Embedded systems. Today RISC Processors has got the
power to meet the needs of the market seemingly.
RISC, REDUCED INSTRUCTION SET
Originated in processor research programs at Stanford and Berkeley
Universities around 1980, the RISC concept was a major influence on
the design of today's processors. Some thoughtful persons argued that while
reducing the semantic gap between the processor instruction set and
the high level language, silicon area was a sacrifice. If we want to
make processor go fast, we must first understand what it spends its
time doing. They actually spend very less time in processing. The
Table will give a better idea.
Instruction Type Typical dynamic Usage
Data Movement 43%
Control Flow 23%
Arithmetic operations 15%
Logical Operations 5%
Others (branching , indexing) 1%
These example statistics suggest that the most important instructions
to optimize are those concerned with data movement, either between the
processor registers ands memory or from registers to registers. These
account for almost half of all the instructions executed. Second most
frequent are the flow control which account for another quarter.
Arithmetic operations are down at 15% as are the comparisons. Now we
can make the ways for making the processors faster. The most important
of these is the pipelining. Another important concept is of cache
memory and third technique, super-scalar instruction execution, which
isn’t used in ARM but generally all latest DSP processors have this.
Examples of RISC machines are IBM 801 minicomputer, VLSI RISC chips
such as RISC I, RISC II and
MIPS (1984 ), and PowerPC (601,
603, 604, 620).