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ARM2 µarch
General Info
Arch Type	CPU
Designer	ARM Holdings
Manufacturer	VLSI Technology, Sanyo
Introduction	1986
Process	2 µm
Core Configs	1
Pipeline
Type	Scalar, Pipelined
Stages	3
Decode	1-way
Instructions
ISA	ARMv2
Cache
L1I Cache	0 KiB/Core
L1D Cache	0 KiB/Core
Succession
ARM1 ARM3

ARM2 is the second ARM implementation designed by ARM Holdings (then Acorn Computers) as a successor to the ARM1. Introduced in 1986, the ARM2 brings a number of major improvements over its predecessor.

Overview

See also: ARM's History

Introduced in 1986, the ARM2 is a reimplementation of the ARM1 on a smaller process along with the addition of a number of additional enhancements. The ARM2 was capable of exceeding 10 MIPS when not bottlenecked by memory with an average of around 6 MIPS. Unlike the ARM1 which was predominantly a research project, the ARM2 became the first commercially successful ARM microprocessor.

The ARM2 was designed to work as an embedded controller or a coprocessor or as a stand-alone microprocessor system. The Acorn Archimedes family of personal computers was built using the ARM2 along with a number of fully custom support chips that were also designed by Acorn Computer.

Process Technology

See also: 2 µm process

ARM2 chips were manufactured by VLSI Technology and Sanyo on a 2 µm double-level metal CMOS process.

Architecture

Key changes from ARM1

• 2 µm process (from 3 µm)
• > 2x MIPS when not bottlenecked by memory
• 27-entry register file (from 25)
  • 2 new program status registers
  • Aid Fast Interrupts
• New support for coprocessors
• New support for hardware multiply and accumulate

New instructions

ARM2 introduces a number of new instructions to deal with the new features:

Coprocessor:

• CDP - Coprocessor data process
• LDC - Load to coprocessor
• STC - Store from coprocessor
• MCR - Move to coprocessor
• MRC - Move from coprocessor

Arithmetics:

• MUL - Multiplication
• MLA - Multiplication and accumulate

Block Diagram

Core

Core

Pipeline

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Die

• 2 µm process
• 27,000 transistors
• ~5.5 mm x 5.5 mm
• 30.25 mm² die size

All ARM2 Chips

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References

• Furber, S. B., and A. R. Wilson. "The Acorn RISC Machine ߞ an architectural view." Electronics and Power 33.6 (1987): 402-405.