ARM innovation gives 32-bit RISC performance at 16-bit system cost
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ARM re-defines RISC Rules to create Thumb
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Cambridge, UK. March 6, 1995 -- Advanced RISC Machines Ltd (ARM)
today announced a powerful extension to the ARM architecture - Thumb.
This gives 16-bit system designers access to ARM's full 32-bit RISC
architecture at 16-bit system costs without compromising performance.

Because of a desire for more sophisticated features, many applications
such as mobile phones, pagers and disk controllers now require more
performance, address space and software support than 8 or 16-bit
controllers can deliver. While 32-bit systems are fast enough, they
may be too expensive for consumer markets, since they require more
memory and a more complex circuit board.

ARM re-applies RISC rules to reduce system cost
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By identifying the critical subset of the ARM instruction set and
encoding it into 16-bits, ARM has succeeded in reducing typical
program size by 30-40% from ARM's already excellent code density.
Since this Thumb instruction set uses less memory for program storage,
cost is further reduced.

All Thumb aware processor cores combine the capability to execute both
the 32-bit ARM and the 16-bit Thumb instruction sets. Careful design
of the Thumb instructions allow them to be decompressed into full ARM
instructions transparently during normal instruction decoding without
any performance penalty. This differs from other 32-bit processors
implementing a 16-bit data bus, which require two 16-bit memory
accesses to execute every 32-bit instruction ('SX' style) and so halve
performance.

Performance is not compromised, flexibility increased
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The patented Thumb decompressor has been carefully designed with only
a small amount of circuitry additional to the existing instruction
decoder, so chip size and thus cost do not significantly increase.
Designers can easily interleave fast ARM instructions (for performance
critical parts of a program) with compact Thumb code to save memory.

Industry analyst James Turley, Senior Editor, Microprocessor Report
said "For price-sensitive embedded applications, Thumb is a clever and
unique solution. It keeps all the advantages of ARM's low-power 32-bit
RISC architecture and adds the benefits of code density that 16-bit
designers expect. Thumb's innovative approach doesn't sacrifice
performance for low cost or low power, but gives embedded system
designers an interesting new choice."

Thumb is fully supported by the ARM Software Development Toolkit
incorporating C compiler and assembler, profiler, instruction accurate
simulator (ARMulator) and a Source Level debugger with graphical user
interface (GUI). Third party tools vendors are also working closely
with ARM to develop a range of software tools for Thumb. ARM offers
Thumb benchmarking services through its consulting operation.

ARM is working with its partners to produce Thumb-aware silicon, with
the first public announcements coming from Cirrus Logic Inc and VLSI
Technology Inc. Development card availability will coincide with the
release of silicon in Q3/95. The first Thumb-aware core will be the
ARM7TDMI macrocell (where the T indicates Thumb), which is destined
initially for custom products in mobile communications and embedded
control.

ARM's Managing Director, Robin Saxby, comments that "The development
of Thumb re-affirms ARM's leadership as the global volume RISC
standard. Complementing last month's announcement of the high
performance StrongARM partnership with Digital, Thumb allows ARM to
serve control applications at significantly lower system costs than
ever before. The ARM Architecture enables a broader range of
applications than any competitive offering at best MIPS/Watt and
MIPS/$ points."

***   Ends   ***


Editorial Notes, Advanced RISC Machines Limited (ARM(TM))
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ARM designs, licenses and markets fast, low cost, low power
consumption RISC processors for embedded control, consumer/educational
multi-media, DSP and portable applications. ARM licenses its
technology to semiconductor partner companies, who focus on
manufacturing, applications and marketing. Each partner offers unique
ARM related technologies and services, which together satisfy a wide
range of application needs. ARM also designs and licenses
peripherals, supporting software & hardware tools and offers design
services, feasibility studies and training. ARM's global partnership
is making the ARM architecture the world's volume RISC standard.
ARM's partners are: VLSI Technology, GEC Plessey Semiconductors,
Sharp, Texas Instruments, Cirrus Logic, Samsung, AKM and Digital
Semiconductor. ARM's shareholders are Acorn Computers, Apple
Computer, VLSI Technology and Nippon Investment & Finance (a Daiwa
Securities subsidiary).

Contacts:

ARM Ltd - Trent Poltronetti
Tel: +44 1223 400449, Fax: +44 1223 400410
e-mail:  trent.poltronetti@armltd.co.uk

Cirrus Logic Inc - Bo Ericsson
Tel: 510 226-2069, Fax: 510 226-2240

VLSI Technology - Tom Schild
Tel: 510 226-2069, Fax: 510 226-2240

ARM, Thumb, StrongARM and the ARM Powered logo are trademarks of
Advanced RISC Machines Ltd.