This section summarizes the basic design requirements for PCI.
1. PCI Local Bus Specification 2.1 (or higher)
| Required |
All cards, bridges, and devices that use PCI must be designed to meet the requirements defined in PCI specification version 2.1 or higher.
2. No ghost cards in system
| Required |
A computer must not include any "ghost cards," which are cards that do not correctly decode transaction Type 1 cycles and so appear on all buses because the ghost card's PCI Configuration Space appears in more than one bus/device/function coordinate. This also includes, for example, devices that ignore some Type 0 transaction bits and therefore appear at multiple device/function addresses.
A PCI card should be visible through hardware configuration access at only one bus/device/function coordinate.
3. Standard method used to close BAR windows on nonsubtractive decode PCI bridges
| Required |
Setting the Base Address Register (BAR) to its maximum value and the limit register to zeroes should effectively close the I/O or memory window referenced in that bridge BAR.
4. PCI docking through a bridge connector
| Recommended |
Microsoft recommends docking through a bridge connector, with the actual bridge on the docking station (not on the mobile unit). The bridge can be positive or subtractive decoding. The bridge should create a new bus number so that devices behind the bridge are not on the same bus number as other devices in the system.
After a warm dock, the BIOS should not configure the bridge nor any other devices in the docking station. That is the responsibility of the operating system.
Microsoft recommends putting the PCI-to-ISA bridge on the docking station, and having no PCI-to-ISA bridge on the mobile unit. Mobile PCs typically have no ISA expansion slots, and the ISA devices on the mobile PC can be controlled by the Plug and Play interface. For more information on requirements for docking station systems, see the "Basic PC 97" chapter in Part 2 of this guide.
Notice that implementing delayed transactions for PCI-to-PCI and PCI-to-ISA docking bridges are required in the PCI 2.1 specification only when certain timing conditions are not met. For PC 97 design requirements, the PCI 2.1 specification is interpreted to mean that delayed transactions are required only when "targets cannot complete the initial data phase within the requirements of this specification," as stated in the PCI 2.1 specification. Delayed transactions are a hardware-related timing issue (and will provide a performance advantage) but are not related to operating system requirements.