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Written by: Ravn
What's the deal with PCI Express?
Date: April 20, 2005
Once upon a time, (really not that long ago) your computer's ability could be partially
gauged by how many PCI slots it had. More PCI slots meant you could cram a lot more into your PC. Over time, more and more of the components that used to take up these slots, (sound cards, video cards and network cards for example) became integrated into the motherboard. High end video cards could still be had in PCI form, but AGP was quickly eating up that market. So suddenly, instead of your computer needing 5 PCI slots, all you needed was 1 AGP. But hey, that's great, right? Less stuff you need to buy, better integration, all good things.
The problem, however, was that anything extra you wanted, (say a gigabit network card, or a 7.1 sound card, or an extra IDE controller card) still required your old PCI slots. PCI has been around for a very long time, and
isn't getting any faster. With video cards on AGP, it seemed like there was no hope for more PCI speed/bandwidth.
Thankfully, hardcore gaming has saved the day once again. Back in the time of 3dfx, folks used to have a video card and a 3d accelerator card (like the Voodoo2). You would daisy-chain these video cards together to gain extra graphics power. With the advent of AGP, this came to an end. Computers only have 1 AGP slot, so you
couldn't hook 2 of your nifty new AGP video cards together. You were stuck. Why not have 2 AGP ports on a computer, you ask? Because AGP is only for video cards. There are no other functions for it. This means that for the 99% of computer users out there, a second AGP port would be a waste of money. So, it never developed. The thing to understand, however, is that companies like
Nvidia want you to buy 2 video cards. Why sell you one, when they can sell you two?
Again though, the hurdle of AGP reared its ugly head. They could always have gone back to regular old PCI cards, however PCI just
didn't have the bandwidth necessary for modern video cards, let alone for multiple ones. PCI needed to be updated. PCI
couldn't just be replaced though. It has been around for so long, and so many people have PCI cards, that it
couldn't just be done away with. Backwards compatibility needed to be maintained.
So, in 2002, PCIe (PCI Express) was introduced. Really there is no comparing it with the old PCI standard. The amount of bandwidth available is so much greater than with PCI as to be ridiculous.. The old PCI standard could support up to a total bandwidth of 512MB/s. PCIe can handle 2.5GB/s easily, and could go as high as 80GB/s.
What about PCI-X?
PCI-X was an attempt to do, essentially what later wound up being done by PCIe. Unfortunately, while it did increase the bus width and the clock rate, it actually made some of the old problems of PCI worse. It could support up to 1GB/s in bandwidth. The problem was that it was very expensive to implement, and the way they made it work (by increasing the clock speed and increasing the bus width) caused it to be extremely sensitive to "noise" (interference) and crosstalk. Not many people adopted this standards, and instead stuck with PCI.
PCIe promises to add years of life to the old PCI standard, as well as allowing many cool new technologies, (and, as in the case of video cards, a revival of some old ones). It is being adopted fairly quickly by many motherboard manufacturers, and can already been found in many of the higher end systems. It
shouldn't be long now before all computers are equipped with some number of PCIe slots.
Written by: Ravn (20th April 2005)
Ravn is a Member of CAAHP |
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This article was imported from the CyberArmy University site. (original author: PixieLuv)
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