Hardware Reference
In-Depth Information
of the 'multi-function I/O' adapter card. The 'bare' system has provision for
the following I/O facilities for:
one or two floppy disk drives (via a 34-way ribbon cable header);
six USB ports (two on the front panel and four on the rear panel);
a first serial port (with its 9-way D-connector fitted to the rear bracket);
an optional second serial port connector (via an 8-way header);
a parallel port (with its 25-way D-connector fitted to the rear bracket);
a game/joystick port (via a 16-way ribbon cable header);
an optional IDE device (via a 40-way ribbon cable header which is not
normally used if IDE facilities are available on the motherboard);
firewire (a high-speed serial bus).
Cooling
All PC systems produce heat and some systems produce more heat than others.
Adequate ventilation is thus an essential consideration and fans are included
within the system unit to ensure that there is adequate air flow. Furthermore,
internal air flow must be arranged so that it is unrestricted as modern processors
and support chips run at high temperatures. These devices are much more prone
to failure when they run excessively hot than when they run cool or merely warm.
Legacy support devices
Each of the major support devices present within a PC has a key role to
play in off-loading a number of routine tasks that would otherwise have to
be performed by the CPU. This section provides a brief introduction to each
generic device together with internal architecture and, where appropriate, pin
connecting details (Table 1.8).
Maths coprocessors
Maths coprocessors, 'numeric data processors' (NDP) or 'floating point units'
(FPU) as they are variously called, provide a means of carrying out mathematical
Table 1.8 Intel legacy support chips originally used with original x86 processors
Processor type
8086
8088
80186
80286
80386
Clock generator
8284A
8284A
On-chip
82284
82384
Bus controller
8288
8288
On-chip
82288
82288
Integrated
82230/82231, 82335
82230/82231, 82335
support chips
Interrupt
8259A
8259A
On-chip
8259A
8259A
controller
DMA controller
8089/82258
8089/8237/82258
On-chip/82258
8089/82258
8237/82258
Timer/counter
8253/8254
8253/8254
On-chip
8253/8254
8253/8254
Maths
8087
8087
8087
80287
80287/80387
coprocessor
Chip select/
TTL
TTL
On-chip
TTL
TTL
wait state logic
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