|
Slot
Types |
Bandwidth
Table |
 |
PCI |
133 Mb/s |
| AGP 8X |
2,100 Mb/s |
| PCI Express 1x |
400 Mb/s |
| PCI Express 4x |
1600 Mb/s |
| PCI Express 8x |
3200 Mb/s |
| PCI Express 16x |
6400 Mb/s |
| IDE (ATA100) |
100 Mb/s |
| IDE (ATA133) |
133 Mb/s |
| SATA |
1500 Mb/s |
| SATA II |
3000 Mb/s |
| Firewire |
400 Mb/s |
| USB 1 |
12 Mb/s |
| USb 2 |
480 Mb/s |
|
Gigabit Ethernet |
1000 Mb/s |
PCI Express
Since PCI Express is a serial
based technology, data can be sent over the bus in two
directions at once. Normal PCI is Parallel, and as such all data
goes in one direction.
Each 1x lane in PCI Express can transmit in
both directions at once. In the table the first number is the bandwidth in
one direction and the second number is the combined bandwidth in both
directions. Also please note that in PCI Express bandwidth is not shared the
same way as in PCI, so there is less congestion on the bus.
The "x" in an
"x16" connection stands for "by." PCIe connections are scalable by one, by
two, by four, and so on.
When the computer
starts up, PCIe determines which devices are plugged into the motherboard.
It then identifies the links between the devices, creating a map of where
traffic will go and negotiating the width of each link.
Each lane of a PCI
Express connection contains two pairs of wires -- one to send and one to
receive. Packets of data move across the lane at a rate of one bit per
cycle. A x1 connection, the smallest PCIe connection, has one lane made up
of four wires. It carries one bit per cycle in each direction. A x2 link
contains eight wires and transmits two bits at once, a x4 link transmits
four bits, and so on. Other configurations are x12, x16 and x32.
PCI
PCI is short for Peripheral
Component Interconnect. The PCI slot is a local system bus standard that was
introduced by the Intel Corporation, however, it is not exclusive to any
form of processors and PCI slots are found in both Windows PCs and Macs.
PCI
slots allow numerous different types of expansion cards to be connected
inside a computer to extend the computers functionality. Examples of PCI
expansion cards are network cards, graphics cards and sound cards.
Although the bus speed is slightly slower than PCI Express, the PCI slots
are the most common type of slot and found on most motherboards today. If
you are installing a new FireMV video card and you are unsure about the
slots, stick with the PCI version of this card it will always work.
Compare PCI and PCI Express
The 32-bit PCI bus has a
maximum speed of 33 MHz, which allows a maximum of 133 MB of data to pass
through the bus per second. Different PCI Express specifications allow
different rates of data transfer, anywhere from 400 MB to 6400 MB of data per
second and beyond. (see table at top of page)
Since
PCI, PCI-X and PCI Express are all compatible, all three can coexist. So far, video cards have made the fastest transition to the PCIe format. Network and sound adapters, as well as other peripherals, have
been slower in development. But since PCIe is compatible with current
operating systems and can provide faster speeds, it is likely that it will
eventually replace PCI as a PC standard. Gradually, PCI-based cards will
become obsolete.
Acknowledgments
to HowStuffWorks, answers.com and Directron for assistance in this article.
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