Lessons from Discarded Computer Architectures - History of Computing: Learning from the Past - page 201

development series moved to the Motorola 68000 and the Apple Macintosh line of
computers. These ran a new operating system with some routines in Read Only
Memory (ROM) for speed. This operating system was called 'System' in 1984, but
gradually became called MacOS. It incorporated elements from FreeBSD's and
NetBSD's implementation of Unix from 1996 [13].
The processors used by Apple changed from the Motorola 68040 series to
PowerPC chips (Motorola and IBM) and then to Intel x86 chips from 2007.

Intel 8086 Motorola 6502

Apple II

Acorn - BBC
micro-computer

IBM PC

PowerPC

ARM RISC processors

Microsoft Windows

Macintosh operating
system based on BSD
Unix and ported to x86
processor family. Dual
booting possible (the
same computer can run
Windows and Mac OS)

Mobile phones use
ARM processors

Pentium
processors

Apple iPad uses a
RISC processor - the
A4.

Intel XScale™
processors

Commentators claim it
incorporates the ARM
Cortex-A9 MPCore
[14,15]

Fig. 2. Development pathways for two dominant personal computer families

It should be noted that all these processor families were von Neumann computers -
with a single processor. This architecture has a single memory store which holds
instruction codes and data. Programs run sequentially, and therefore an algorithmic
approach is highly congruent with such machines. Fortunately many problems can be
solved by such methods, and the high speed (3GHz is not uncommon) of processor
operation supports a wide range of useful functions.
An alternative was offered by the Transputer from Inmos [16] from 1983 [17]. In-
mos Limited was a British semiconductor company, founded by Iann Barron, based in