10.3 PCI Express (PCIe)
The main technical inovation of PCI Express is a serial data transmission compared to the parallel interfaces
of other computer bus systems like ISA, PCI and PCI-X.
PCI Express defines a serial point-to-point connection, the so-called Link:
Selectable Width
D
ev
ic
e
A
D
ev
ic
e
B
Ref. Clock
Ref. Clock
The data transfer within a Link is done via Lanes, representing one wire pair for sending and one wire pair for
receiving data:
TX
Logic
D+
Component A
Component B
D+
V
BIAS
V
BIAS
D-
D-
RX
Logic
RX
Logic
TX
Logic
This design leads to a full duplex connection clocked with 2.5 GHz capable of transfering a data volume of 250
MB/s per lane in each direction. Higher bandwith is implemented by using multiple lanes silmutaneously. A
PCI Express x16 slot for example uses sixteen lanes providing a data volume of 4 GB/s. For comparison: when
using conventional PCI the maximum data transfer rate is 133 MB/s, PCI-X allows 1 GB/s but only in one
direction respectively.
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Date: 28th March 2018
GPS180PEX