Page 39 - DCAP103_Principle of operating system

Principles of Operating Systems

Notes Figure 1.9: A typical SMP system. Three processors are connected to the
same memory module through a bus or crossbar switch.

CPU CPU CPU

BUS OR CROSSBAR

MEMORY
DISK

Asymmetric Multiprocessing
Asymmetric multiprocessing varies greatly from the standard processing model that we see in
personal computers today. Due to the complexity and unique nature of this architecture, it was
not adopted by many vendors or programmers during its brief stint (1970–1980). Whereas a
symmetric multiprocessor or SMP treats all of the processing elements in the system identically,
an ASMP system assigns certain tasks only to certain processors.
Asymmetric hardware systems commonly dedicated individual processors to specific tasks. For
example, one processor may be dedicated to disk operations, another to video operations, and
the rest to standard processor tasks. These systems do not have the flexibility to assign processes
to the least-loaded CPU, unlike an SMP system.

Although hardware-level ASMP may not be in use, the idea and logical process is still commonly
used in applications that are multiprocessor intensive. Unlike SMP applications, which run their
threads on multiple processors, ASMP applications will run on one processor but outsource
smaller tasks to another. Although the system may physically be an SMP, the software is still
able to use it as an ASMP by simply giving certain tasks to one processor and deeming it the
“master”, and only outsourcing smaller tasks to “slave “processors.

Prepare a list of system requirements before installing an operating system.

1.8 Hardware ASMP

1.8.1 Overview

Asymmetrical multiprocessors are defined by the characteristic that each processor is unique
(non-symmetrical). It is common to have one processor that has access to the memory map as a
whole, and other processors which simply act as slaves to the main or master processor. Usually,
these slave processors will have their own memory which is not tied to the primary processors
memory. Slave processors are required to exchange data with the main processor through a
partitioned segment of memory that is allocated solely for the purpose of communication.
Depending on the hardware in question, each processor may or may not be able to speak to
other processors directly.
1.8.2 Differences between Hardware ASMP and SMP

In the symmetrical multiprocessing design, each processor is able to access the entire memory
map; there are no master or slave processors. In this case each processor is non-unique and has
equal power. This means that they can share memory between themselves and can interact with

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