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For more information about the general DDI changes that the new 1394 bus driver supports, see Device Driver Interface (DDI) Changes in Windows 7.

Last update 1 Jan.

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The 1394ohci.sys bus driver is a single (monolithic) device driver, implemented by using the kernel-mode driver framework (KMDF).

Ieee 1394 Host Controller Drivers That Were

The legacy 1394 bus driver (available in earlier versions of Windows) includes multiple device drivers that were implemented by using the Windows Driver Model (WDM) in a portminiport configuration.

The 1394ohci.sys bus driver replaces the legacy port driver, 1394bus.sys, and the primary miniport driver, ochi1394.sys.

This topic describes some of the known differences in behavior between the new and the legacy 1394 bus driver.

Ieee 1394 Host Controller Install A 1394

It is automatically loaded when you install a 1394 controller.

This is not a redistributable driver that you can download separately.

This behavior differs from that of the legacy 1394 bus driver, in which certain IO requests complete immediately.

The legacy 1394 bus driver uses asynchronous quadlet reads at S100 speedor 100 megabits per second (Mbps).

The 1394ohci.sys bus driver also uses the values that are specified in generation and maxrom entries of the nodes configuration ROM header to improve the retrieval of the remaining content of the configuration ROM.

For more information about how the new 1394 bus driver retrieves the contents of a nodes configuration ROM, see Retrieving the Contents of a IEEE 1394 Nodes Configuration ROM.

This requirement is due to the 1394ohci.sys bus drivers exclusive use of short (arbitrated) bus resets.

This device extension is described by the NODEDEVICEEXTENSION structure.

In 1394ohci.sys, this structure remains at the same location as in the legacy 1394 bus driver, but the nonstatic members of the structure might not be valid.

When a client driver uses the new 1394 bus driver, they must make sure that the data accessed in NODEDEVICEEXTENSION is valid.

The static members of NODEDEVICEEXTENSION that contain valid data are Tag, DeviceObject, and PortDeviceObject.

All other members NODEDEVICEEXTENSION are nonstatic, which the client driver must not reference.

For example, if the system that is running 1394ohci.sys has a host controller that complies with IEEE 1394b but all devices on the bus comply with IEEE 1394a, then the new 1394 bus driver tries to optimize the gap count.

If a node sets both of the bits in the speed (sp) field in the self-id packet, then 1394ohci.sys considers the node to comply with IEEE-1394b.

If the speed field contains any other value, then 1394ohci.sys considers the node to comply with IEEE-1394a.

The gap count value that is used is based on table E-1 in the IEEE-1394a specification, which provides the gap count as a function of hops.

You can change the default gap count behavior by using a registry value.

For more information, see Modifying the Default Behavior of the IEEE 1394 Bus Driver.