Introduction

In this edition of Upgrading to the Next Generation PC, we’re going to be looking at graphics cards and graphics interface technologies.

The Upgrading to the Next Generation PC series is based on the video series of the same name. So if you can’t be bothered reading about it, watch it here. In this article, however, we’ve given a lot more detail than the video.

The GPU or graphical processing unit is the processing chip on a graphics card – the chip that does all the hard work to render, manipulate and display images on your computer screen. The graphics card itself houses the GPU, these days usually under large fans or heatsinks. Also under all that cooling you’ll find memory modules that help the GPU store information for processing. The graphics card also of course has an interface for its connection to the motherboard in the computer, interfaces such as AGP and PCI Express which we will discuss in a moment. In a multi-GPU situation, more than one GPU can be on the one graphics card, or more than one graphics card can be installed in the one system. As you’re probably aware, there are two main GPU manufacturers, NVIDIA and ATI (now owned by AMD).

Removing an Old Graphics Card

In the PC we’re upgrading in this series, there’s an old AGP 8X graphics card. To remove a graphics card from a system, unplug the power (if there is a power cord going to it). Also check to see if there is a little security clip interface on the back of the AGP or PCI Express slot on the motherboard. Plus, you’ll need to unscrew or un-clip the back plate that slots into the back of the case. Then simply pull the card out.


AGP versus PCI Express

PCI Express is the current and therefore the “next generation” graphics technology in the context of this series. When we talk about the upgrade, AGP is the old standard that we’ve removed from the PC.

If you’re upgrading a PC that is around 5 years old, most likely that it’ll have an AGP card in it. When you go into a shop to upgrade your graphics card most likely you’re not going to be able to. They’ll ask ‘do you have an AGP slot or a PCI Express slot?’ If it’s AGP, there’s not much point in upgrading. It’s not that you can’t get any AGP graphics cards anymore, you can, but they’re usually slower versions than PCI Express graphics cards. They are bottle-necked and the reason they’re bottle-necked is because of the bandwidth available to PCI Express versus AGP.

Bandwidth is the amount of data that travels through a particular path, in this case, between the GPU, CPU and RAM.

AGP 8X ended with 2GB/s maximum data transfer rate.  PCI Express 2 is 0.5GB/s per lane. On a 16 lane card, that’s a total of 8GB/s. Let’s look at it this way … we’ll convert every 0.5 of a GB into a car. That means that AGP can fit four cars down its single road at the same time. One issue with this is that the road has no individual lanes. Hopefully along the way, the cars don’t end up interfering with each other since there’s nothing to direct them, although they do fit down that single unmarked road. PCI Express, with a 16 lane card, can actually fit 16 cars down its 16 individual lanes. Since all the cars are in their individual lanes, there is no chance that the cars can interfere with each other. So not only do more cars reach the end of the road at the same speed but they do it more efficiently.

There’s also a physical difference between an AGP card and a PCI Express card. In the photo above you can see an HIS Radeon HD 4850 PCI Express card and on top is the old AGP card. You’ll notice that the actual connector on the AGP card is quite different to the one on the PCI Express card.