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Edinburgh University
Computer Science Department
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Advanced Personal Machine
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$p The Computer Science Department's Advanced Personal Machine is a
modular computer system designed to allow easy experimentation with
both hardware and software.
$p Hardware components are connected by a general-purpose, moderate
performance bus.
These components are either memories or complete processors.
The simplicity of the bus enables a large variety of different processors
to be connected to the system.
The performance of the bus is sufficient to allow a modest number of
these processors to be active concurrently.
Programs running on the processors communicate through the mutually
accessible memory.
$p In general, Input and Output devices are not connected directly to the
system bus but are controlled by special processors.
These processors communicate with the rest of the system.
This approach allows such processors to be programmed to present a high
level Input/Output interface to the other components.
$p To complement the hardware, similarly modular software is being
developed.
This will allow new hardware components to use software already available
on existing hardware components.
Thus when experimenting with, for example, processor architecture, it will
not be necessary to write basic software such as a filing system in order to
exercise the new hardware.
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$p At present, only the first basic hardware modules have been fully developed.
These are:
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The Control Processor.
This provides basic I/O connections to a VDU and a local area communications
network station.
The control processor is based on a Motorola M68000 microprocessor and in itself
provides a satisfactory basis for a powerful personal computer.
In more developed systems, the control processor will take on the task
of providing the necessary initialisation and control facilities for
the rest of the system.
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The Ethernet Interface.
This is an interface to a local area communications network,
through which access is provided to shared facilities -- in
particular to a central filestore.
It was developed locally and is based on the Xerox 'Ethernet' packet
broadcast network.
It transmits data at 2M bits per second.
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Memory
A 1/2M Byte memory board has been implemented.
$p Additionally several experimental graphics interfaces have been built.
Bus arbitration units allowing multiple processors to share the bus have
also been built.
$p 25 of these systems are currently under construction for use
within the Department.
There is also significant interest from similar establishments both
inside and outside the University of Edinburgh.