Acorn  Acorn A4 Laptop

Acorn A4 Laptop

The A4 Laptop is the only portable computer produced by Acorn. It is based on the A5000 and has the size of an A4 sheet of paper, hence the name. The A4 came with a carrying case that had room for the external power supply, the mouse and the manuals. The display was gray scale, and the machine had maximum of 14 displayable shades of gray. It could however also be connected to a VGA screen for higher resolution and color display.

The Acorn A4 came equiped with the ARM3 CPU at 24MHz, 24MByte of RAM, a 3.5" Floppy disk drive, and a 120MByte hard drive option. The sound capabilities were the same as the other Acorn machines, 8 voice stereo sound. The machine had the following ports:

  • Centronics
  • RS232-C
  • Stereo Sound
  • Mouse port
  • VGA Connector
  • External Keyboard

The A4 ran Risc OS 3.10 that was located in a 2MByte ROM chip.

Acorn Archimedes Computers

The Acorn Archimedes computer was the commercially available computer to use the RISC (Reduced Instruction Set CPU) architecture. The first models were launched in 1987, and Acorn developed updated models of the machines until the early 1990's. The CPU in the Acorn machines is the ARM chip, which stands for Acorn RISC Machine. ARM Chips are still used today, one popular example is the iPhone.

Arthur Operating System

The Acorn Archimedes computers were initially shipped with the Arthur OS, but could be upgraded to RISC OS, by replacing the ROM chips that contained the operating system. Because of these ROMs, the computer would boot immediatly into it's GUI, similar to the Atari ST line of computers. This gave them a significant advantage over PC's that loaded the operating system from disk.

The early Archimedes computers used the Arthur operating system, which was replaced in 1989 with RISC OS. RISC-OS featured co-operative multitasking, task management, solid window manipulation, adaptive rendering of bitmaps and coloring, and above all stability that the Arthur OS lacked. New applications quickly started to take advantage of the RISC-OS resulting in mature software such as Acorn Desktop Publisher, and even a PC Emulator.

Source WikiPedia


ARM, an acronym for Advanced RISC Machines (originally Acorn RISC Machines) is a Reduced Instruction Set Computer (RISC) cpu architecture. The ARM1, uses a 32-bit internal structure, but only had a 26-bit address space, limiting the processor to 64MByte of memory. This limit was removed in the ARMv3 series, which introduced a full 32-bit address space.

The first machine that used the ARM chip was the BBC Micro, it used the ARM as a secondary processor at 6MHz.

The result of the simulations on the ARM1 boards led to the late 1986 introduction of the ARM2 design running at 8 MHz, and the early 1987 speed-bumped version at 10 to 12 MHz. The ARM2 was roughly seven times the performance of a typical 7 MHz 68000-based system and twice as fast as an Intel 80386 running at 16 MHz.

The ARM2 featured a 32-bit data bus, 26-bit address space and 27 32-bit registers, of which 16 are accessible at any one time (including the Program Counter). The ARM2 had a transistor count of just 30,000, compared to Motorola's 68000 model with around 68,000. This simplicity enabled the ARM2 to have low power consumption, yet offer better performance than the Intel 80286.

A successor, ARM3, was produced with a 4 KB cache, which further improved performance. The address bus was extended to 32 bits in the ARM3.

source: WikiPedia
Technical Details
Released 1992 Country United Kingdom Brand Acorn Computers Ltd. Type Acorn Archimedes 3000+ Name Acorn A4 Laptop CPU Class ARM CPU ARM3 @24MHz RAM 4MB Sound Chip Integrated Sound 8 channel, 8-bit stereo sound. Display Chip VIDC1A Video Display Processor Display 132x30 Text
640x480 14 shades of gray (LCD Screen)
1152x896 (VGA Screen)
Best Text 132x30 Best Color none Best Graphics 1152x896 Sprites 1 hardware sprite (pointer) System OS RISC OS 3.10 Storage 3.5" Internal Disk Drive, 120MByte optional hard drive Original Price £1395
Related Systems
Acorn BBC/Acorn 8-bit
Acorn Archimedes 300/400
Acorn New Archimedes 400s
Acorn Workstations
Acorn Archimedes 3000+
Acorn  A4 Laptop (1992)
World Wide Web Links
Acorn Computers
A list of all Acorn machines
History of RISC OS
Wikipage about the history of the RISC Operating System
Wikipage about the ins and outs of the RISC Operating System