Pci Express Card Interoperability; 75 Watt And 150 Watt Pci Express Slots - HP BL680c - ProLiant - G5 Introduction Manual

The PCI Express specification also defines two other PCI-like form factors. A PCI Express Mini Card,
similar to the Mini PCI card will include a x1 connector for use in portable products. The ExpressCard
is similar to PCMCIA cards and will include a x1 PCI Express connector and a USB 2.0 connector for
use in desktop and portable products (Figure 8).
Figure 8. PCI Express Mini Card (left) and ExpressCard (right) form factors

PCI Express card interoperability

The PCI Express specification provides for significant interoperability features between PCI Express
add-in cards and slots. Up-plugging (for example, a x4 card into a x8 slot) is supported. Additionally,
the specification also supports down-shifting, which allows the creation of slots with larger physical
connectors that are wired for a smaller logical link to the server's I/O hub. For best performance, of
course, a card should be used in a slot that supports its logical link size; however the availability of
down-shifted slots provides the flexibility to use larger cards (for example, x8) in slots with smaller
logical links if necessary.
Table 1. PCI Express add-in card interoperability
x4 Connector
x4 Link
x4 Card x4 Operation
x8 Card Not Allowed
x16 Card Not Allowed
It is HP's design philosophy to provide larger connectors whenever possible. Most slots with x4 links
have x8 connectors and slots with x8 links come with x16 connectors, thus delivering maximum
flexibility. Connector and link width for the slots should be documented on the hood label of each
ProLiant server.

75 Watt and 150 Watt PCI Express slots

In general, the PCI Express specification calls for slots to support up to 25-watt power consumption for
each add-in card. In order to support the emerging high performance add-in cards that consume more
than 25 watts of power, the specification also supports the concept of a 75-watt slot. Slots rated for
75 watts are distinguishable from others by the required increase in spacing around them which is
needed to dissipate the additional heat associated with the higher power consumption.
x8 Connector x8 Connector
x4 Link x8 Link
x4 Operation x4 Operation
x4 Operation x8 Operation
Not Allowed Not Allowed
x16 Connector x16 Connector
x8 Link x16 Link
x4 Operation x4 Operation
x8 Operation x8 Operation
x8 Operation x16 Operation
8