PCI Express™ Card Electromechanical Specification Revision 1.1

This specification is a companion for the PCI Express Base Specification, Revision 1.1.  Its primary focus
is the implementation of an evolutionary strategy with the current PCI desktop/server mechanical
and electrical specifications.  The discussions are confined to ATX or ATX-based form factors.  
Other form factors, such as PCI Express Mini Card are covered in other separate specifications.   5
1.1. Terms and Definitions
Add-in card A card that is plugged into a connector and mounted in a chassis  
slot.    
ATX A system board form factor.  Refer to the ATX Specification,  
Revision. 2.2.  10
ATX-based form factor Refers to the form factor that does not exactly conform to the  
ATX specification, but uses the key features of the ATX, such as  
the slot spacing, I/O panel definition, etc.  
Auxiliary signals Signals not required by the PCI Express architecture but necessary  
for certain desired functions or system implementation, for   15
example, the SMBus signals.  
Basic bandwidth  Contains one PCI Express Lane
x1, x4, x8, x16 x1 refers to one PCI Express Lane of basic bandwidth; x4 refers to a  
collection of four PCI Express Lanes; etc.
Down-plugging Plugging a larger Link card into a smaller Link connector; for example,   20
plugging a x4 card into a x1 connector3025