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ARM Hardware Overview
Programmer's Reference Manuals
» Part 1 - Introduction
» ARM Hardware
» Overview
Overview
RISC OS was developed to take advantage of the ARM microprocessor for a range of high end personal computers. The ARM processor was originally designed by Acorn Computers Ltd, but is now developed by ARM Holdings Ltd.
RISC OS was designed for the ARM processor which is a RISC chip. i.e It is a processor with a comparatively small set of instructions. This is one of the reasons why ARM chips can run code very efficiently.
Since the original development of the ARM processor back in 1985, many more have been developed. The original processor was the ARM 2. This was followed shortly by the ARM 3, ARM 610, ARM 700 and the StrongARM. Several ARM system-on-chips (SOCs) with integrated memory controller and video controller were also used.
Processor Types
RISC OS supports numerous ARM processors. The table below highlights the some of the processors supported by RISC OS.
| Type | ~MIPS | ARM architecture | Extra Notes |
|---|---|---|---|
| ARM 2 | 4 – 5 | ARM v2 | - |
| ARM 250 | 7 | ARM v2as | - |
| ARM 3 | 13.5 | ARM v2as | 4Kbyte on-chip cache |
| ARM 610 | 23 | ARM v3 | Address bus and Program counter to use full 32-bit width and extra privileged processor modes |
| ARM 700 | 35 | ARM v3 | - |
| ARM 7500 | ? | ARM v3 | Integrated memory and video controller, plus 4k cache |
| ARM 7500FE | ? | ARM v3 | Integrated memory and video controller, plus 4k cache and includes hardware Floating Point support |
| StrongARM | 235 | ARM v4 | Separate caches for data and instructions |
| Xscale | ? | ARM v5 | - |
| Cortex-A8 | ? | ARM v7 | Superscalar processor with extension for handling multimedia and signal processing (NEON technology is 128-bit SIMD extensions) |
RISC OS Hardware
The hardware of RISC OS computers can be categorised as follows:
| Category | ARM architecture | Models |
|---|---|---|
| Archimedes | ARM v2 & ARM v3 | A305, A310, A310M, A410, A440, BBC A3000, A410/1, A420/1, A440/1, A540, A5000. A4, A3010, A3020, A4000 |
| RiscPC | ARM v3 & ARM v4 | A7000, Risc PC, Kinetic Risc PC |
| HAL(Hardware Abstraction Layer) | ARM v3 and above | Iyonix, Cortex-A8 port |