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Leopard Technical Q&As: Hardware & Drivers
Core Audio's Hardware Abstraction Layer (HAL) acts as the interface between an audio device driver and an audio application. The HAL supports native multichannel audio in a manner that is scalable to future high-resolution formats. Developers can create audio devices compatible with Apple products and use HAL and I/O Kit APIs to create software to access audio devices.

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Allocating and sharing memory with user space from an I/O Kit driver (HTML) (日本語 HTML)
QA1197: Describes the preferred technique for allocating and sharing buffers in an I/O Kit kernel driver.
Generating a Non-Maskable Interrupt (NMI) (HTML) (日本語 HTML)
QA1264: Explains how to generate a non-maskable interrupt (NMI) on modern Macintosh systems.
Retain Counts of io_object_t Objects in IOKit.framework (HTML) (日本語 HTML)
QA1195: Distinguishes between the retain counts of an I/O Kit kernel object and its io_object_t user space proxy.
IODeviceTree and the I/O Registry (HTML) (日本語 HTML)
QA1120: Describes the IODeviceTree plane in the Mac OS X I/O Registry.
The "packages" node in the device tree (HTML)
HW90: Describes the "packages" node in the Open Firmware device tree.
Obtaining the name of an external MIDI Device from a MIDI Endpoint (HTML)
QA1374: Get the names of external MIDI Devices from MIDI Endpoints.
Available FireWire Isochronous Bandwidth (HTML)
QA1356: Discusses attempting to "pre-flight" an isochronous bandwidth allocation request by reading the currently available bandwidth.
Installing an I/O Kit KEXT Without Rebooting (HTML)
QA1319: Describes the state of the art of installing I/O Kit kernel extensions (KEXTs) without requiring a restart.
Power Management; Policy Maker vs. Power Controller (HTML) (日本語 HTML)
QA1121: Describes the differences between a Power Management Policy Maker and a Power Management Power Controller.
IOKit Framework Headers (HTML) (日本語 HTML)
QA1107: Describes the differences between the headers in IOKit.framework and the I/O Kit headers in Kernel.framework.
Are the Name Registry device tree nodes unique? (HTML)
Deprecated - HW64: Discusses whether Name Registry nodes copied from the Open Firmware device tree are unique.
What are configuration variables in Open Firmware? (HTML) (日本語 HTML)
HW38: Defines the configuration variables in Open Firmware.