Disclosed is a methodto operate regular/older PCI devices dynamically in PCI-X mode. Benefits include maximizing frequency without the need for hardware changes.

Background

Currently, to take advantage of the PCI-X specification and capabilities, all devices attached to the PCI-X bus must be capable of PCI-X transactions. However, many motherboards only contain regular PCI devices. By default a device that is not PCI-X-aware will reduce the PCI bus speed to 33MHz or 66MHz regardless of presence of PCI-X devices.

General Description

The PCI/PCI-X switching mechanism involves the software configuration of simple hardware control digital logic that must be present on the motherboard of a PC system. The following components are required:

1. The hardware of this mechanism is a few discrete TTL gates.� Such logic can always be used with existing motherboard components as part of the Super I/O and/or South bridge of the main chipset (see Figure 1).

2. The software is the assembly x86 instructions integrated in the system BIOS to control the hardware logic.

The disclosed method regains the PCI-X capability of the bus by isolating the on-board PCI device(s) (via software). In this way the end user can optionally disconnect the on-board regular PCI device and install a PCI-X device that runs at maximum speed. (100MHz or 133MHz).

Typically a hard reset or power cycle is required for the host PCI-bridge to switch between...