Intel responded with the development of AGP, or Advanced Graphics Port. This advanced helped to free up the PCI bus, which was becoming overly congested with 3D graphics, and allowed for video bandwidth at rates that were 4 times faster than PCI was capable of. With the introduction of AGP, Intel single-handedly enabled the visual computing revolution. Now, 6 years after that initial launch of AGP, so much has changed. Today's AGP is in its 3rd revision, and is capable of speeds that are 16 times faster than PCI - and still, that's not enough. Today's PCI and AGP archetecture is becoming overloaded. 3D graphics are demaning ever more bandwidth, and the old PCI bus is being expected to handle more than ever before: 3D audio, gigabit networking, firewire, ATA-133, USB, and more. So, with this in mind, the industry set to developing a 3rd Generation IO format, or 3GIO. The fruit of that labor is PCI Express; and its getting ready to replace PCI and take general IO connectivity to the next level. The designers of PCI Express had a number of challenges that they had to overcome in order for PCI Express to meet all of the expectations of a next generation IO solution:
In addition to these features, a number of other advanced features were incorporated:
One of the more important improvements is PCI Express's ability to scale speeds by aggregating links to form multiple lanes. This means that you can make a PCI Express connector faster simply by increasing its length (essentially adding more connections). This is all done with comeplete transparency to the other layers - so no special support is required. In this manner, PCI Express can support speeds of 1x, 2x, 4x, 8x, 12x, 16x, and 32x. Graphics adapters based on PCI Express technology will be using the 16x mode - meaning that you will get troughput of about 40.0 Gigabits per second in each direction (that's about 4 Gigabytes per second at peak) - as compared to the ~2.128 Gigabytes per second that we see now from 8X AGP. With even more performance as the technology develops. So, what does the future hold for computers using PCI Express? Well, first off, the PCI that we know and love so well will not die right away (the same cannot be said for AGP however). Next generation motherboards will likely support both PCI and PCI Express side by side by means of an additional header placed at the end of a standard PCI slot to support lower bandwidth (1 and 2 lane) PCI Express devices; somewhat similar to the extra connector used for 66 MHz PCI devices. This, combined with the full software support will allows for a seamless integration with older PCI technology. Moving farther into the future, we will see PCI Express based technology replace PC cards in notebooks, and begin to make the idea of a modular computer a real possibility. The big names
in the computer industry like Intel, NVIDIA, Microsoft, and AMD have already
thrown their support behind PCI Express. With supporters like that, it
seems to be a pretty sure thing that the PCI Express I/O system will be
the new standard for many years to come. |