Hardware Reference
In-Depth Information
Figure 4.43. Typical configuration of 32-bit 33MHz PCI slots in relation to ISA or EISA and
AGP slots.
The PCI specification identifies three board configurations, each designed for a specific type of
system with specific power requirements; each specification has a 32-bit version and a longer 64-bit
version. The 5V specification is for stationary computer systems (using PCI 2.2 or earlier versions),
the 3.3V specification is for portable systems (also supported by PCI 2.3), and the universal
specification is for motherboards and cards that work in either type of system. 64-bit versions of the
5V and universal PCI slots are found primarily on server motherboards. The PCI-X 2.0 specifications
for 266 and 533 versions support 3.3V and 1.5V signaling; this corresponds to PCI version 2.3,
which supports 3.3V signaling.
Note
You can find pinouts for the 5V, 3.3V, and universal PCI slots on the disc in the Technical
Reference section.
Figure 4.44
compares the 32-bit and 64-bit versions of the standard 5V PCI slot to a 64-bit universal
PCI slot.
Figure 4.45
shows how the connector on a 64-bit universal PCI card compares to the 64-bit
universal PCI slot.
Figure 4.44. A 32-bit 33MHz PCI slot (top) compared to a 64-bit 33MHz PCI slot (center) and a
64-bit universal PCI slot that runs at 66MHz (bottom).
Figure 4.45. A 64-bit universal PCI card (top) compared to the 64-bit universal PCI slot
(bottom).
Notice that the universal PCI board specifications effectively combine the 5V and 3.3V
specifications. For pins for which the voltage is different, the universal specification labels the pin V
I/O. This type of pin represents a special power pin for defining and driving the PCI signaling rail.
Another important feature of PCI is the fact that it was the model for the Intel PnP specification.
