PCI Bus Pin Out, [Parallel Bus]

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PCI Bus pinout for both 32 bit and 64 bit cards is shown below;
Signal Pins 63-94 are only used on 64 bit PCI bus cards. The PCI pinout for the 32 bit bus stops at the key-way [Spacer], while the 64 bit pinout occupies the entire table. The PCI local bus was used in personal computers to provide expansion slots for add-on cards to the motherboard. The PCI bus replaced the ISA PC-AT expansion slot in PCs.
The PCI local bus is not the same as the new PCI Express bus which has a completly different pinout.

Peripheral Component Interface Pinout

The number sign in the pinout table below refers to: "A # symbol at the end of a signal name indicates that the signal’s asserted state occurs when it is at a low voltage. The absence of a # symbol indicates that the signal is asserted at a high voltage.

The Time Multiplexed Address and Data bus may exist as either 0 to 31 bits (32bits) or 0 to 63 bits (64bits) using the 64 bit expansion bus. Both the Address and Data line use the same bus, Address first then Data. 32 bit PCI may also use 64 bit addressing by using two address cycles; termed Dual Address Cycles (DAC), the low order address is sent first. Additional control bits are utilized once the bus is increased to 64 bits.

The specification defines both a Reset line and a Clock line. The Clock may be either 33MHz or 66MHz. I believe the 66MHz clock rate is only defined for the 64bit bus width.
A number of 'Handshake' lines exist to allow communication, i.e. Ready, and Acknowledge, see pinout above.

Two Parity lines are made available, one for the 32 bit bus width (bits 0 to 31) and an additional one for the 64 bit expansion (bits 32 to 63). Two error bits; I assume, 1 for the LSB 32 bits and one for the upper 32 bits.

The pinout listings showing (+5 V or +3.3 V) mean: In a +5 volt system the pins are +5 volts, in a +3.3 volt system the pins are +3.3 volts.

Back to the main PCI Bus page, or the PCI Board Dimension page PCI Card Size or Personal Computer bus page.

The Peripheral Component Interface 'PCI' Bus was originally developed as a local bus expansion for the PC (ISA) bus. The PCI spec defines the Electrical requirements for the interface. No bus terminations are specified, the bus relies on signal reflection to achieve level threshold. The first version of the PCI bus ran at 33MHz with a 32 bit bus (133MBps), the current version runs at 66MHz with a 64 bit bus. The PCI bus operates either synchronously or asynchronously with the mother board bus rate. While operating asynchronously the bus will operate at any frequency from 66MHz down to (and including) 0Hz. Flow control is added to allow the bus to operate with slower devices on the bus, allowing the bus to operate at their speed. PCI is an unterminated bus, the signal relay on signal reflections to attain there final value.

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