ARM’s Race to Embedded World Domination

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Lack of Buoyancy Prevents Archimedes’s Atlantic Crossing

Many North American computer enthusiasts first became aware of Acorn and ARM from a 1987 article about the Acorn Archimedes A310 PC in Byte Magazine [3]. The Archimedes was based on ARM2, a second generation of the original ARM design. The ARM2, also known as the VL86C010, was basically just a shrink to a 2.0 um CMOS process. A block diagram of the ARM2 is shown in Figure 1. The shrink reduced the die size to about 30 mm2 and increased the processor clock rate to 8 MHz.


Figure 1: Block Diagram of ARM2/VL86C010

The ARM2 and Archimedes appeared around the same time as the first IBM compatible PCs built around the Intel 386DX, but used a much simpler unified memory architecture, or UMA, system design with no caches and CPU driven graphics. Despite the simpler and potentially much less expensive RISC processor and UMA system architecture, the Archimedes A310 was quite competitive in performance with 386-based PC’s as can be seen in Table 1 [4].

Table 1. Performance of Archimedes A310 and Contemporary PCs

Program

Acorn

Archimedes

8 MHz

IBM PS/2

Model 80 (386)

16 MHz

Compaq

Deskpro 386

16 MHz

Apple

Mac II (68020)

15.67 MHz

Dhrystone (Dhry/s)

4901

3626

3748

2083

Fibonacci (sec)

52.4

57.3

53.1

83.7

Sieve (sec)

5.7

6.5

6.0

16.7

Sort (sec)

10.0

7.74

5.6

22.4

Savage (sec)

91.2

9.5

21.5

5.4

The RISC-based A310 excelled on integer programs, but the lack of FPU showed up in the ‘Savage’ benchmark, where slow IEEE-754 compatible emulation routines in the C library hurt the performance. Remarkably, the A310 could run Savage in interpreted BASIC in 32.8 seconds, only about 50% slower than the Compaq Deskpro 386 equipped with a 80287 math coprocessor.

The A310 ran an operating system called Arthur. It was based on earlier OS Acorn wrote in 1979 for the BBC Micro, a 6502-based PC. Arthur was quite modern for a PC and included features like modularity between the OS and file system (two different file systems were supported), a graphical user interface (GUI) called Desktop, and a built in scripting language.


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