Sun Microsystems Enterprise 250 Owner's Manual page 115

Older PCI cards operate at 5 VDC, while newer cards are designed to operate on
3.3 VDC. Cards that require 5 volts will not operate in 3.3-volt slots, and 3.3-volt
cards will not operate in 5-volt slots. "Universal" PCI cards are designed to operate
on either 3.3 volts or 5 volts, so these cards can be inserted into either type of slot.
The system provides three slots for 5-volt cards and one slot for a 3.3-volt card.
All four PCI slots accept universal cards.
Most PCI cards operate at clock speeds of 33 MHz, while some newer cards operate
at 66 MHz. All four PCI slots can accept 33-MHz cards. 66-MHz cards are restricted
to the slot labelled PCI66-0.
The table below shows the mapping of the PCI slots to the two PCI buses, and the
type of PCI cards supported in each slot.
TABLE 5–1
Rear Panel Connector
Slot Number Label
3 PCI66-0
2 PCI33-2
1 PCI33-1
0 PCI33-0
The following figure shows the PCI slots on the main logic board.
Slot Width
(bits)/
Card Type
PCI Bus (bits)
1 64 / 32 or 64
0 64 / 32 or 64
0 64 / 32 or 64
0 64 / 32 or 64
DC Voltage/
Clock Rates
(MHz) Card Type
33 and 66 3.3 V & Univ
33 5 V & Univ
33 5 V & Univ
33 5 V & Univ
Hardware Configuration
81