Information Technology Reference
In-Depth Information
tems require a great deal of local electronic memory to operate.
3.
Graphics adaptor
. The graphics adaptor can be a major limiting factor on the perform-
ance of a system. New interfaces, such as AGP, considerably speed-up graphics per-
formance. Another limiting factor is the amount of local memory on the graphics adap-
tor. The more memory, the higher the resolution that can be used, and the more colours
that can be displayed. AGP is overcoming this limiting factor, as it allows the main elec-
tronic memory to be used to store graphics images.
4.
Cache capacity
. Cache memory has caused a great increase in the performance of a
system. If a cache controller makes a correct guess, the processor merely has to examine
the contents of the cache to get the required information. A level-1 cache is the fastest
and is typically connected directly to the processor (normally inside the processor pack-
age), and the level-2 cache is on the motherboard.
5.
Hard disk capacity/interface
. The hard disk typically has an affect on the running of a
program, as the program and its component parts must be loaded from the disk. The in-
terface is thus extremely important as it defines the maximum data rate. SCSI has fast
modes which give up to 40 MB/s, while IDE gives a maximum rate of 33 MB/s. The ca-
pacity of the disk also can lead to problems as the system can use unused disk capacity
of a virtual memory capacity.
Obviously, applications that are more specific will be affected by other factors, such as:
•
Internet access
. Affected mainly by the network connection (especially if a modem is
used).
•
CD-ROM access
. Affected by the interface to the CD-ROM.
•
Modelling software
. Affected by mathematical processing.
•
3D game playing
. Affected mainly by the graphics adaptor and graphics processing
(and possibly the network connection, if playing over a network).
2.8
Practical PC system
At one time PCs were crammed full of microchips, wires and connectors. These days they
tend to be based on just a few microchips, and contain very few interconnecting wires. The
main reason for this is that much of the functionality of the PC has been integrated into sev-
eral key devices. In the future, PCs may only require one or two devices to make them oper-
ate.
The architecture of the PC has changed over the past few years. It is now mainly based on
the PCI bus. Figure 2.22 shows the architecture of a modern PC. The system controller is the
real heart of the PC, as it transfers data to and from the processor to the rest of the system.
Bridges are used to connect one type of bus to another. There are two main bridges: the sys-
tem controller (the north bridge), and the bus bridge (the south bridge).
