The pixels you're now reading on your computer monitor are being refreshed at
rates of 30 to 70 times per second. Although your screen is mainly black and
white as you read this, it is potentially capable of producing up to 16.7
million different colours. And while your PC is probably not operating at top
speed as you scan this article, it's likely capable of reaching data-transfer
rates of one gigabyte per second. All these impressive figures are attributable
to one hardware component in your computer: the graphics card.
Strictly speaking, the data-transfer rate of one gigabyte per second is
performed by the actual application you're using. As you use a software program,
it sends your commands to the computer's hardware, translating what your fingers
type into the letters and numbers that appear on the screen before you.
Once the computer receives your keyboard commands, it shares them among its
graphics card and its central processing unit (CPU). The graphics card is a
sophisticated piece of hardware that includes its own store of RAM (random
access memory) in order to perform its function of bringing images to life on
your screen. There is a separate stash of RAM in the heart of your computer
itself, which hangs onto your work as you fiddle with it; and this graphics-card
RAM does essentially the same thing, while remaining dedicated to graphical data
only. The graphics card can carry 16MB (megabytes) to 64MB of RAM (your PC's
share of RAM is usually between 64MB and 128MB). Graphics-card RAM stores
information that is not going onscreen instantaneously.
Once the graphics card holds the data destined for your monitor, it gets
together with the CPU to make pictures that will light up your screen. The
commands you type into your keyboard are received by the graphics card as binary
code -- digital zeroes and ones that must be translated into the analog signals
your screen can deal with. Before that information is translated into analog
form, the graphics card and CPU enact two phases -- the transform and lighting
phase, and the set-up phase.
The transform and lighting phase takes information from the software program
you're using to assemble the screen's pixels and create lighting effects among
them. The transform and lighting phase is often performed by the computer's CPU
rather than its graphics card; although newer, flashier cards are able to handle
even this part of the proceedings. From there, the graphics card always takes
over to enact the set-up phase, in which the pixels stipulated in the previous
step become plotted to particular points on the monitor. The first phase handles
the colour, shade, and interlock of the pixels; the second phase oversees where
on your screen those pixels appear.