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ARM1 µarch
General Info
Arch Type	CPU
Designer	ARM Holdings
Manufacturer	VLSI Technology
Introduction	1985
Process	3 µm
Core Configs	1
Pipeline
Type	Scalar, Pipelined
Stages	3
Decode	1-way
Instructions
ISA	ARMv1
Cache
L1I Cache	0 KiB/Core
L1D Cache	0 KiB/Core
Succession
ARM2

ARM1 was the first ARM microarchitecture implemented by ARM Holdings (then Acorn Computers) as a research and development project for the BBC Computer Literacy Project. ARM1 was introduced in 1985 and was extended to be used as a coprocessor in the Acorn's BBC Micro microcomputers. ARM1 was distributed as an evaluation system and was never commercialized.

History

Main article: ARM's History

The ARM1 (Acorn RISC Machine 1) is Acorn Computers' first microprocessor design. The ARM1 was the initial result of the Advanced Research and Development division Acorn Computers formed in order to advance the development of their own RISC processor. The ARM instruction set design started in 1983. A reference model was written in BBC BASIC by Sophie Wilson and Steve Furber in just 808 lines of code. On April 26 1985, after 6 man-years of design effort, the first ARM processor prototype was delivered. The first batch of prototypes were functional and were shipped to customers in the form of evaluation systems. At that time the ARM1 was the simplest RISC processor produced.

The first prototype tested worked on the first try, this was despite the ammeter reading no power. The prototype test board designed was faulty with a short. The chip was entirely running off the leakage from the I/Os. Designed to run at 1 W, the chip averaged under 100 mW typical power.

Process Technology

See also: 3 µm process

ARM1-based chips were manufactured by VLSI Technology on a 3 µm double-level metal CMOS process.

Architecture

Overview

• Goal 1.5x performance of the VAX 11/780
• 3 µm process
• 26-bit address space
• Pipeline
  • Very simple
  • 3-stage
  • No hardware multiplication
  • 25 32-bit registers
    • 16 For user
    • 9 For supervisor
  • 4 Modes
    • User, Supervisor, IRQ, FIQ

Block Diagram

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Core

Pipeline

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Die Shot

• 3 µm process
• 24,800 transistors
• ~6,000 gates
• ~7 mm x 7mm
• 50 mm² die size
• PLCC-82
  • 74 signal pins
  • 8 power/ground pins

All ARM1 Chips

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References

• ARM hardware reference manual, ARM Evaluation System, Acorn OEM Products, August 1986

Documents

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