64-Bit Kernel Support

64-bit FireWire kernel (and user) services are fully functional in Snow Leopard. Some layers above FireWire do not yet work, such as the audio driver AppleFWAudio.kext. All other major services are available, including IOFireWireIP, Mass Storage (SBP-2), iSight, and DV/MPEG. The stack should be fully usable for both kernel and user space driver development. However, some high-level applications that use DV or MPEG on FireWire may not work, due to support issues in other software layers.

FireWire sample code and tools (such as in AVS) are functional for DV and MPEG. FireWire hard drives should be reliable, though some user-interface quirks may be present. For example, the drive may not be visible in Finder or System Profiler, but works correctly in Terminal.

FireWire kernel programming interfaces are basically identical in the 64-bit and 32-bit kernels, except that pointers are 64 bits wide in the 64-bit kernel. FireWire user space programming interfaces should be 100% compatible with the 32-bit and 64-bit user space programming interfaces in OS X v10.5.

FireWire kprintf and FireWire KDP (kernel debugger protocol) are both available in 64-bit kernel mode.

Integrated FireWire KDP

FireWire KDP (kernel debugger protocol) allows developers to perform two-machine debugging over FireWire. In Snow Leopard FireWire KDP is now built in, so installing AppleFireWireKDP.kext is no longer required (however, you can still find AppleFireWireKDP.kext at /Developer/Extras/Kernel Debugging).

To enable FireWire KDP on a target machine, enter this command in Terminal:

sudo nvram boot-args="debug=146 kdp_match_name=firewire"

For more information on FireWire KDP, including the FireWireKDPProxy, see the files at /Developer/Extras/Kernel Debugging or download the latest FireWire SDK from ADC Development Kits.

New Buffer-Fill Isochronous Receive Service

The FireWire Family now has kernel programming interfaces that provide an alternate isochronous receive service. This new service uses the multi-channel buffer-fill DMA mode of the 1394 OpenHCI (Open Host Controller Interface). It allows for receiving packets on more isochronous channels then there are available DMA contexts. It also eliminates the need to write a DCL program to receive isochronous packets. (The old isochronous receive services are unchanged and still fully supported.)

The new programming interfaces are part of the IOFireWireController object. For more details, see IOFireWireMultiIsochReceive.h. Note that user-space access to these programming interfaces is not yet available.