PCI Express is a serial connection that operates more like a network than a bus. Instead of one bus that handles data from multiple sources, PCIe has a switch that controls several point-to-point serial connections.  These connections fan out from the switch, leading directly to the devices where the data needs to go. Every device has its own dedicated connection, so devices no longer share bandwidth like they do on a normal bus.

PCI Express Lanes

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. This identification of devices and connections is the same protocol PCI uses, so PCIe does not require any changes to software or operating systems.
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.

Devices using PCI share a common bus, but each device using PCI Express has its own dedicated connection to the switch.

Below is a table comparing the main specifications for the expansion for expansion slots that ever exists for the PC.

Slot

Clock

Number of Bits

Data per Clock Cycle

Bandwidth

ISA

4.77 MHz

8

1

4.77 MB/s

ISA

8 MHz

16

1

8 MB/s

MCA

5 MHz

16

1

10 MB/s

MCA

5 MHz

32

1

20 MB/s

EISA

8.33 MHz

32

1

33.3 MB/s (16.7 MB/s typically)

VLB

33 MHz

32

1

133 MB/s

PCI

33 MHz

32

1

133 MB/s

PCI-X 66

66 MHz

64

1

533 MB/s

PCI-X 133

133 MHz

64

1

1066 MB/s

PCI-X 266

133 MHz

64

2

2132 MB/s

PCI-X 533

133 MHz

64

4

4266 MB/s

AGP x1

66 MHz

32

1

266 MB/s

AGP x2

66 MHz

32

2

533 MB/s

AGP x4

66 MHz

32

4

1066 MB/s

AGP x8

66 MHz

32

8

2133 MB/s

PCIe 1.0
x1

2.5 GHz

1

1

250 MB/s

PCIe 1.0
x4

2.5 GHz

4

1

1000 MB/s

PCIe 1.0
x8

2.5 GHz

8

1

2000 MB/s

PCIe 1.0
x16

2.5 GHz

16

1

4000 MB/s

PCIe 2.0
x1

5 GHz

1

1

500 MB/s

PCIe 2.0
x4

5 GHz

4

1

2000 MB/s

PCIe 2.0
x8

5 GHz

8

1

4000 MB/s

PCIe 2.0
x16

5 GHz

16

1

8000 MB/s

PCIe 3.0
x1

8 GHz

1

1

1000 MB/s

PCIe 3.0
x4

8 GHz

4

1

4000 MB/s

PCIe 3.0
x8

8 GHz

8

1

8000 MB/s

PCIe 3.0
x16

8 GHz

16

1

16000 MB/s

分类: Hardware

1 条评论

Kevin · 07/19/2013 10:20 上午

Good

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