Specifications

PCI or PCI-X Expansion Slots

The following sections define the PCI and PCI expansion requirements.

PCI Only

Some configurations of the Power Mac G5 support three 64-bit 33 MHz PCI slots that interface to the K2 I/O.

The PCI configuration conforms to the PCI Specification 2.3.

PCI-X Only

Some configurations of the Power Mac G5 support three PCI-X slots that interface to the HyperTransport bus

via the PCI-X bridge. One slot runs at a maximum of 133 MHz and two slots run at a maximum of 100 MHz.

The 133 MHz slot can support a maximum burst bandwidth of 1064 MBps, based on 64 bits times 133 MHz.

The two 100 MHz slots can support a combined bandwidth of 800 MBps. It is recommended that the highest

bandwidth card be inserted in the 133 MHz PCI-X slot labeled slot 4.

Note: Dual PCI-X card sets work best if installed in slots that are running on the same bus, i.e. the

100 MHz bus.

The PCI-X configuration conforms to the PCI-X Specification 10B.

PCI and PCI-X

To optimize performance of both PCI and main memory transfers, your PCI card should use DMA. The

point-to-point G5 architecture is designed to provide optimal performance to each subsystem using DMA. If

your card does not support DMA, it should use vector data types for read/write transfers. This approach results

in 4 dword burst transfers on the PCI bus.

Important: The Power Mac G5 does not support marking memory space on PCI cards as cacheable. This

technique was used in the past to improve read/write performance for cards without an on-board DMA

engine. Cards using this technique will not function on the Power Mac G5.

The computer’s case has four openings in the back for access to I/O connectors on cards in the three expansion

slots and the AGP slot. Each slot has room for a full size 12.335-inch or short 6.926-inch card. The numbering

on the casing is 1 through 4 and corresponds to the label on the PCB. Number one is the AGP slot and numbers

two through four are the PCI or PCI-X slots.

Expansion

PCI or PCI-X Expansion Slots