HP 3000 Manuals

General Information Manual

The Advantages of Simplicity 

Reducing processor complexity allows for several key advantages when
compared with complex instruction set computer architectures.
Compatibility, lower cost, and higher performance are all direct benefits
of the reduced complexity approach of PA-RISC.

Compatibility 

Compatibility has always been a cornerstone of the HP 3000 product
strategy, and maintaining compatibility when moving to the
next-generation HP 3000 systems was a critical design consideration.  A
simple instruction set is ideal for emulating more complex instruction
sets; hence, the reduced complexity of PA-RISC allows for compatibility
of nonprivileged mode object code as well as source code.  When moving
from the MPE V-based systems to the
900 Series systems, emulation of the MPE V-based HP 3000 instruction set
allows object code to be run "as is"; this is called compatibility mode.
Source code can simply be recompiled to exploit the full native mode
performance potential of the 900 Series system.  For detailed information
on MPE V migration, please refer to Chapter 3, "The HP 3000 Operating
System".

Lower cost 

Eliminating much of the hardware complexity associated with conventional
computer systems directly translates into a reduced part count and a
system that is easier to design, to develop, and to manufacture.  The
result is a system that costs less to bring to market, and this cost
saving is directly reflected in the superior price/performance of the 900
Series systems.

Higher performance potential 

With the 900 Series systems, the performance potential of a wide variety
of semiconductor technologies is maximized.  For example, the Series
980/100, implemented in VLSI technology, delivers performance typically
achieved by conventional systems only through use of more costly, less
dense ECL semiconductors.  With PA-RISC, a given level of performance can
be achieved at a cost significantly lower than with conventional systems.


          Figure A-2.  Higher Performance Potential 

Allows for a broad family of systems 

The reduced amount of processor circuitry associated with a RISC-based
design is ideal for development of fast, single-chip microprocessors that
can be used to develop cost-effective computers.  And at the high-end of
the HP 3000 family, the performance advantage of PA-RISC, coupled with
the ability to support multiprocessor systems, delivers very
high-performance solutions with power comparable to today's water-cooled
mainframes.

Ideal for advancing technologies 

The simplicity of PA-RISC makes it ideal for maximizing benefits from
advancing hardware technologies such as very large scale integrated
(VLSI) components.  Hewlett-Packard has long enjoyed a leadership
position in using high-performance, high-density semiconductors, and this
experience has been used to great effect in the 900 Series systems.
Processor performance can be maximized by placing an entire CPU on a
single chip, thus keeping signal delays short and allowing CPU cycle time
to be decreased.  With further integration, such as placing CPU and
processor caches on-chip, instruction and data access times can also be
minimized, providing additional performance gains.

Higher processor reliability 

Just as requiring fewer parts to build a processor directly results in
decreased cost, it also implies that there are fewer parts to fail.
Thus, PA-RISC systems provide increased processor reliability.  In
addition, PA-RISC is designed to support future extensions for providing
higher system availability.  For example, future versions of
multiprocessor systems could support the capability of redundant
processors, such that if one processor failed, another could
automatically take its place, allowing the system to continue operating
without interruption.

MPE/iX 5.0 Documentation