Buss speed

Consider the buss a highway system in your computer where information (or data), travels to and from components. The technical definition of a buss states it must connect multiple lines of data, whereas a single line of data would be a port. For the sake of this article, I will discuss all lines of data in a computer as a buss.

Everything in your computer communicates. When you activate a program, it leaves the hard drive and enters the main system RAM via the IDE, SATA or SCSI “buss” for fast access by the processor. When video or sound cards are present, the relevant data is sent to the relevant card to alleviate stress off the processor.

When certain components talk about a bit rate (example: 16bit/24bit/64bit/128/256 ect.) that is referring to how much information can travel through the buss at one time.  This is most commonly seen in processor or video card architecture.

The buss speed in any given system is a critical statistic and involves an awful lot of attention. Let’s say you buy a new video card for your PC. You check to see if your motherboard has an PCI (Peripheral Component Interconnect) or PCIe (e for express, a faster PCI slot because it has a larger buss speed. There is also Gen2 PCIe which increases the buss speed even higher), which is a buss for video data connected directly to the processor. You call your local computer shop and buy a mid level video card. Excitedly, you pick up a few graphics intensive games and install it. What factors will determine how happy you will be with the performance of this card?

• The processors FSB (Front Side Buss, the processors personal buss for data to get into the processor itself) must be able to accept the amount of data the video card will be giving it. The video cards job is to make the processors life easier, but it can just as easily cause bottle necking and make it much harder for the most overworked component in your PC.
  

• The motherboards internal transfer. Everything is controlled by the motherboard, if its not up to par your whole system will suffer. Be wary of builders that will not disclose what motherboard they are using when you ask. Some do not display the motherboard for a chosen computer because it can vary depending what components choices you choose when buying the PC, so always ask.
  

• The speed and CL rating of your RAM. Your RAM has to be able to not only allocate enough data to the video card to make sure you utilize all the performance you can, it also has to be able to accept all the data sent back out by the video card. Speed of the RAM is important, but CL is more important in most cases. Read RAM for more details.

Example: You have a video card capable of sending out 20 bits of data per second. You motherboard can transfer 15 and your processor can handle 35. The processor will be fine, it has more then enough speed to handle all the information from the video card and the RAM, but the video card will slow the whole process down with bottlenecks. The video card will be told to give the processor all it can, in this case 20 bits of data. When the 20 bits try to get to the processor they will be slowed to 15. That will not make the video card slow down, in fact, it will keep trying to send the information making the newer information wait to get though. This will cause a long line to form and lag the PC.

Note: I just chose numbers for this example to make a point. Motherboards today can transfer multiple GBs of data and most clearly mark the speed of each port. You see a SATA 3GB/s, that is a SATA port that transfers at 3GB per second. Same with PCI. A PCI slot, normally 1.1, transfers 250mb per second. A PCI X4 transfers at 1000mb per second, or 250mb per each of the four data lines. 1000mb = 1GB, so the above PCI slot has a 1GB/s transfer. PCIe X16 has a 4GB/s and "Gen2" or "Version 2.0" PCIe has 5GB/s.

Now we could get into the speed of the RAM in this scenario also, but you get the idea. The components in a computer are all very sensitive and extremely technical, they have needs. The same video card can give varying results in every computer it goes into. This is why benchmarks and hardware reviews are not always the best way to go. Then you have to take into account the software controlling the components themselves. This will greatly affect buss speeds and components ability to do their job. From the BIOS to the drivers, and finally the OS (Operating System) there are hundreds of variables that go into performance. Then you have to determine what you want that PC to perform well in. A well built computer will be able to do all tasks, but will always perform better at certain tasks then others, there is no way to avoid this.

I would also like to mention, that buss speed will be one of the most noticeable improvements on a PC. You would hardly notice an increase of 500MHz in processor power, but would immediately notice even a small increase in buss speed. (Based on a well balanced PC, each PC is different and has different needs.)

Where to now? Articles on computer components - How to Choose a PC