Information Technology Reference
In-Depth Information
10
Games Port, Keyboard and Mouse
10.1 Introduction
PCs have traditionally been difficult to connect to and set up, for reasons such as:
•
Different connectors - there are so many different types of connectors for many different
types of devices that connect to the PC. For example, the keyboard uses a 5-pin DIN
plug, the parallel port uses a 25-pin D-type connector, the primary serial port uses a 9-
pin D-type connector, the video adaptor uses a 15-pin D-type connector, and so on. The
future is likely to bring a standardisation of these connectors, possibly with the USB
port.
•
Different configurations - typically different peripherals required assigned interrupts
and I/O addresses. For example, the keyboard uses IRQ1 and I/O ports at 60h and 64h.
This is now being overcome by busses such as SCSI and USB, which only require a sin-
gle interrupt and a limited range of addresses. They also cope better with hot plug-and-
play devices and operating system configurable devices.
•
Different data traffic rates - relatively low speed interfaces, such as the ISA bus, have
often reduced the rate of other faster busses, such as the PCI bus. This is now being
overcome by the use of bridges and the USB bus.
The games port, the keyboard and the mouse are also relatively slow devices which, in their
standard form, all have different connectors. In the future PCs may standardise these low-
and medium-speed devices on the USB port. The keyboard port and mouse port are now
standard items on a PC, and most PCs now have a games port, which supports up to two joy-
sticks.
Most PCs support either a PS/2-style mouse or one connected to the serial port (COM1:
or COM2:). The operating system automatically scans all the mouse and keyboard ports to
determine where the mouse is connected to, and whether there is a keyboard connected.
Typically, these days, a mouse connects to the PS/2 port, which is basically an extension
of the keyboard port. The keyboard connects to either a 5-pin DIN plug, or more typically on
modern PCs to a smaller 5-pin plug. With the smaller connector, the PS/2 mouse and the
keyboard can share the same port (this is typical in new PCs and also for notebooks).
10.2 Games port
The PC was never really designed to provide extensive games support, but as it is so general
purpose, it is now used to run arcade style games. A mouse is well designed for precise
