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Technical Q&As are short question and answer formatted pages that provide answers to questions frequently received at Apple Developer Technical Support.

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Can you explain the words "begin" and "again"? (HTML)
HW70: Explains the Forth looping words "begin" and "again" and how to escape such a loop.
Hardware & Drivers 1999-10-11
Changing the configuration variable in Open Firmware (HTML) (日本語 HTML)
HW40: Tells how to change the configuration variable in Open Firmware.
Hardware & Drivers 1999-02-15
Changing the TCP Window Size (HTML)
NW47: Describes how to change the TCP window size in Open Transport.
Hardware & Drivers 1997-03-14
Checking for the Printer Driver (HTML)
Deprecated - DV42: Describes a legacy Mac OS technique avoiding system hangs when using serial drivers on USB systems.
Hardware & Drivers 2000-06-19
The "chosen" node in the device tree (HTML)
HW88: Describes how to find the "chosen" node in the Open firmware device tree.
Hardware & Drivers 2000-09-05
Clearing mDNSResponder's cached records (HTML)
QA1310: Clearing the Bonjour service cache (mDNSResponder's cached records) for testing purposes.
Hardware & Drivers 2004-02-11
Common QA and Roadmap for USB Software Development on Mac OS X (HTML)
QA1370: Roadmap for development of USB Software on Mac OS X and some Common Questions and Answers
Hardware & Drivers 2006-02-28
DDR SDRAM ICs for PowerBooks and iBooks that use Memory bus slewing (HTML)
QA1344: Specifies DDR SDRAM IC optimization for PowerBooks and iBooks that use Memory bus slewing.
Hardware & Drivers 2004-03-18
Detecting a CD-ROM (HTML) (日本語 HTML)
DV18: Demonstrates CD-ROM drive detection.
Hardware & Drivers 1997-01-31
Detecting specific ROM-in-RAM Mac (HTML) (日本語 HTML)
Deprecated - HW49: Identifying a Mac by name ("iMac"), and better alternatives for determining specific features ("has Firewire").
Hardware & Drivers 1999-10-05
Determining Open Firmware version (HTML)
HW100: Demonstrates how to find out the version of Open Firmware on your Macintosh.
Hardware & Drivers 2000-10-06
Determining RAM size & location in New World Machines (HTML)
QA1065: Demonstrates Open Firmware method of determining RAM size & location in New World Machines.
Hardware & Drivers 2001-08-01
Determining the version of Open Firmware on your Mac (HTML) (日本語 HTML)
HW60: Describes a method to display the version of Open Firmware on a Macintosh.
Hardware & Drivers 1999-03-29
Difference between an Open Firmware word and method (HTML) (日本語 HTML)
HW46: Describes the differences between an Open Firmware word and an Open Firmware method.
Hardware & Drivers 1999-02-15
Difference between using Restart or Shut Down in the Finder's Special menu in Open Firmware (HTML) (日本語 HTML)
HW47: Explains the differences between using Restart or Shut Down on Open Firmware
Hardware & Drivers 1999-02-15
Disabling Processor Cores on a Multi-Core System (HTML) (日本語 HTML)
QA1141: Describes how to disable processor cores on a multi-core system for testing purposes.
Hardware & Drivers 2008-09-16
Discovering all advertised Bonjour service types (HTML)
QA1337: Explains how to discover all Bonjour service types being advertised on the local network.
Hardware & Drivers 2004-06-01
Displaying PCI Configuration Registers contents in Open Firmware (HTML)
QA1036: Demonstrates how to display PCI Configuration Resister contents in Open Firmware.
Hardware & Drivers 2001-05-18
dl command in 1 machine mode (HTML) (日本語 HTML)
HW51: Describes using the "dl" command in 1 machine mode.
Hardware & Drivers 1999-03-29
Do PowerBooks have a PCI bus? (HTML) (日本語 HTML)
HW43: Explains that a Powerbook has a PCI bus.
Hardware & Drivers 1999-02-15
DR Emulator Caches (HTML) (日本語 HTML)
Deprecated - HW28: Describes the Dynamic Recompiling emulator's cache, including a description of when to flush the cache.
Hardware & Drivers 1996-04-08
DRAM DIMM power pin connections for Macintosh Computers (HTML) (日本語 HTML)
QA1271: Discusses design considerations for DRAM DIMM power pin connections for Macintosh Computers.
Hardware & Drivers 2003-07-04
The dreaded "incompatible flag -framework" error (HTML)
QA1096: Explains how to eliminate the incompatible flag -framework error in Project Builder.
Hardware & Drivers 2001-12-05
Empty Memory Objects (HTML) (日本語 HTML)
QA1259: Describes how two memory management edge cases are handled by the common Mac OS memory allocators.
Hardware & Drivers 2003-04-21
Energy Star PCI Device (HTML) (日本語 HTML)
QA1108: Provides useful information for developers of Energy Star-compliant PCI devices.
Hardware & Drivers 2002-01-15
Explanation of SDRAM configuration Nomenclature (HTML)
HW75: Explains the three-part "Device configuration" numbers for SDRAM in the Power Mac G4 Computer Developer Note.
Hardware & Drivers 1999-10-18
ExpressCard Prevents System Sleep (HTML)
QA1517: Describes how some ExpressCard cards can prevent system sleep and how to fix the problem.
Hardware & Drivers 2007-02-28
Faster DDR DRAM in the 867MHz Power Mac G4 (Mirrored Drive Doors) (HTML) (日本語 HTML)
QA1191: Confirms the use of faster DDR DRAM in the 867MHz Power Mac G4 (Mirrored Drive Doors).
Hardware & Drivers 2002-08-19
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.
Hardware & Drivers 2008-10-13
Getting a List of Drivers & LUNs (logical unit numbers) (HTML)
Deprecated - DV04: Describes a legacy Mac OS technique for obtaining a list of SCSI Parallel drivers, devices, and LUNs.
Hardware & Drivers 1995-07-01
Getting a Packet Trace (HTML) (日本語 HTML)
QA1176: Lists tools available for looking at the network packets on the wire.
Hardware & Drivers 2008-06-03
The "green" PCI bus (HTML)
HW93: Explains why the PCI bus is considered "green".
Hardware & Drivers 2000-09-05
HID Manager Event Data Underruns (HTML)
QA1038: Explains how to correctly handle HID Manager event queue data underruns.
Hardware & Drivers 2001-06-13
How can I tell if a PCI device has on board I/O space? (HTML)
QA1287: Demonstrates "how to" tell if a PCI device has on board I/O space.
Hardware & Drivers 2003-09-24
How do I change the numeric base for the Open Firmware user interface? (HTML)
HW66: Explains how to change the numeric base for the Open Firmware user interface.
Hardware & Drivers 1999-10-11
How do I determine the top of the Open Firmware dictionary? (HTML)
HW69: Explains how to determine the top of the Open Firmware dictionary.
Hardware & Drivers 1999-10-11
How does Open Firmware generate the name property? (HTML) (日本語 HTML)
HW39: Describes the Open Firmware name property generation process.
Hardware & Drivers 1999-02-15
How many PCI header types exist today? (HTML)
HW92: Briefly describes the three PCI header types defined in the PCI 2.2 specification.
Hardware & Drivers 2000-09-05
How to use the OT modem script engine (HTML) (日本語 HTML)
Deprecated - NW50: Shows how to use the Open Transport modem script engine.
Hardware & Drivers 1997-07-11
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.
Hardware & Drivers 2003-10-28
Installing smart card reader drivers (HTML)
QA1359: Updates obsolete information contained in the pcscd(8) man page on Mac OS X Jaguar and Panther.
Hardware & Drivers 2004-08-30
Invoking the Open Firmware user interface (HTML) (日本語 HTML)
HW45: Describes how to invoke the Open Firmware user interface on startup.
Hardware & Drivers 1999-02-15
IODeviceTree and the I/O Registry (HTML) (日本語 HTML)
QA1120: Describes the IODeviceTree plane in the Mac OS X I/O Registry.
Hardware & Drivers 2008-09-18
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.
Hardware & Drivers 2002-01-15
IOLog and Interrupt Context (HTML) (日本語 HTML)
QA1100: Describes when IOKit runs at primary (hardware) interrupt context.
Hardware & Drivers 2002-02-13
iSight - Configuring gain settings for IIDC cameras (HTML)
QA1421: Discusses how to configure features of IIDC cameras, specifically gain for the iSight
Hardware & Drivers 2005-04-06
Issues with boot time KEXT loading (HTML) (日本語 HTML)
QA1087: Explains how to solve problems with loading KEXTs at boot time.
Hardware & Drivers 2004-01-15
Legacy Devices (HTML)
HW84: Discusses why legacy devices with hard-wired I/O addresses may not work properly with Open Firmware.
Hardware & Drivers 2000-03-20
Locating the 1275-1994 Standard Document (HTML)
HW85: Alerts that the Open Firmware (IEEE 1275-1994) document can't be found at the IEEE Standards Association site.
Hardware & Drivers 2000-07-17
Making sense of IOKit error codes (HTML) (日本語 HTML)
QA1075: Explains how to interpret I/O Kit error codes.
Hardware & Drivers 2002-02-07
Maximum Memory for the "Firewire" PowerBook (HTML)
Deprecated - HW83: Discrepancies between PowerBook Developer Note and TIL articles 14870 and 58582, regarding maximum memory configurations.
Hardware & Drivers 2000-03-13
Menu Bar Clock and NVRAM (HTML)
QA1102: Explains why booting with the Command-Option-P-R keys doesn't reset date and time preferences.
Hardware & Drivers 2001-12-21
Mixing link-local IP addresses and routable IP addresses (HTML)
QA1357: Explains how to enable communication between devices with link-local addresses and devices with routable addresses.
Hardware & Drivers 2005-07-06
New PPD keywords available in Mac OS X version 10.3 (HTML)
QA1352: Describes the new PPD keywords available for CUPS filters in Mac OS X 10.3.
Hardware & Drivers 2004-05-26
Obtaining the name of an external MIDI Device from a MIDI Endpoint (HTML)
QA1374: Get the names of external MIDI Devices from MIDI Endpoints.
Hardware & Drivers 2004-12-01
Open Firmware device tree nodes (HTML)
HW86: Explains the usage of the "@n" notation in Open Firmware device tree nodes.
Hardware & Drivers 2000-09-05
Open Firmware Memory bus speed (HTML)
HW97: Describes a method to display memory bus speed for G3 or G4 Macintosh in Open Firmware.
Hardware & Drivers 2000-09-22
Open Firmware version number (HTML)
HW96: Discusses the unique values of Open Firmware version numbers.
Hardware & Drivers 2000-09-22
OTScheduleDeferredTask When Task Running (HTML) (日本語 HTML)
NW52: Describes what happens when you use OTScheduleDefferedTask to schedule a task that is running.
Hardware & Drivers 1997-10-13
The "packages" node in the device tree (HTML)
HW90: Describes the "packages" node in the Open Firmware device tree.
Hardware & Drivers 2006-02-22
PC100 SDRAM DIMMs on the Flat Panel iMac (HTML) (日本語 HTML)
QA1130: Describes PC100 SDRAM DIMM limitations on the "original " Flat Panel iMac.
Hardware & Drivers 2002-03-18
PCI address/data stepping (HTML)
HW94: Explains that Apple does not support PCI address/data stepping.
Hardware & Drivers 2000-09-05
PCI bus on the iMac (HTML) (日本語 HTML)
HW42: Explains that the iMac has a PCI bus even though it has no expansion slots.
Hardware & Drivers 1999-02-15
PCI class codes (HTML)
HW91: Explains why PCI class codes are important.
Hardware & Drivers 2000-09-05
PCI Header types (HTML)
HW78: Describes the three required types of PCI headers to be provided in its configuration header space.
Hardware & Drivers 1999-11-15
PCI Macintoshes and CardBus controllers (HTML)
HW87: Explains why older PCI Macintoshes do not recognize a Cardbus controller.
Hardware & Drivers 2000-09-05
PCI SIG (HTML) (日本語 HTML)
HW55: Describes the meaning of the acronym PCI SIG.
Hardware & Drivers 1999-03-29
PCI/PCI-X slots on the Power Mac G5 (HTML)
QA1307: Discusses installing PCI/PCI-X cards of different speeds in the Power Mac G5.
Hardware & Drivers 2003-09-30
Power adapter Sensing for the 17" PowerBook (HTML) (日本語 HTML)
QA1266: Details Design and detection considerations for 17-inch PowerBook power adapters
Hardware & Drivers 2003-06-12
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.
Hardware & Drivers 2002-02-13
PrepareMemoryForIO in the NewWorld (HTML)
DV33: Explains the correct use of PrepareMemoryForIO on DMA buffers when writing a device driver for DMA software.
Hardware & Drivers 1998-12-07
Programmatically causing restart, shutdown and/or logout (HTML) (日本語 HTML)
QA1134: Describes how to programmatically cause restart, shutdown, sleep or logout.
Hardware & Drivers 2008-09-24
Reducing the size of Physical Memory in Open Firmware (HTML)
QA1099: Describes how to configure the Power Macintosh so less memory is recognized than is actually present.
Hardware & Drivers 2001-12-20
Registering a Bonjour service multiple times (HTML)
QA1311: Explains why registering the same Bonjour service twice on the same machine doesn't cause a name conflict.
Hardware & Drivers 2003-10-23
Resetting NVRAM to factory defaults (HTML)
QA1103: Describes what happens when you boot holding the Command-Option-P-R keys.
Hardware & Drivers 2001-12-21
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.
Hardware & Drivers 2008-09-24
A SCSI little secret (HTML)
HW81: Details what to expect when accessing the motherboard SCSI bus on the Blue & White G3.
Hardware & Drivers 1999-12-20
SDRAM Problems With Self-Powered USB Devices (HTML) (日本語 HTML)
HW82: Alerts that non-compliant, self-powered USB devices plugged into a G4, can cause problems with low-voltage-sensitive SDRAM .
Hardware & Drivers 2003-08-21
SDRAM, CAS Latency for the (HTML)
QA1071: Describes the supported CAS Latency values for the "QuickSilver", PowerMac G4 CPUs.
Hardware & Drivers 2001-09-13
Sending SCSI or ATA commands to storage devices (HTML) (日本語 HTML)
QA1179: Explains that Mac OS X does not implement SCSI or ATA pass-through for many mass storage devices.
Hardware & Drivers 2005-05-10
Sequence Grabber - Determining the capture resolution of an IIDC device (HTML)
QA1403: Discusses how to determine the resolution of a captured image from an IIDC device
Hardware & Drivers 2005-01-06
Serial API Choice (HTML)
DV39: Discusses the choice of serial APIs supported by traditional Mac OS and Mac OS X.
Hardware & Drivers 2001-07-02
Sleep vs. Doze on Mac OS X (HTML)
QA1309: Discusses and demonstrates sleep versus doze detection on Machintosh Mac OS X
Hardware & Drivers 2003-10-09
Specifiying if the CPU or the GPU should be used for rendering. (HTML)
QA1416: Which processor will be used for rendering in Core Image and how to affect it.
Hardware & Drivers 2005-08-16
The state of mDNSResponder (HTML)
QA1339: Explains how to obtain information regarding the internal state of mDNSResponder.
Hardware & Drivers 2006-10-03
Stopping Forth command scrolls (HTML) (日本語 HTML)
HW57: Describes how to limit Forth commands from scrolling off the screen.
Hardware & Drivers 1999-03-29
Switching between one and two machine mode for the Open Firmware user interface (HTML) (日本語 HTML)
HW37: Explains how to change from one machine mode to two in the Open Firmware user interface.
Hardware & Drivers 1999-02-15
T_DATA_REQ vs M_DATA TPI Message Blocks (HTML) (日本語 HTML)
NW42: Explains why OT passes data to a TPI module using M_DATA message blocks instead of M_PROTO+T_DATA_REQ.
Hardware & Drivers 1996-10-25
TCP/IP Option Sizes (HTML) (日本語 HTML)
NW62: Enumerates the TCP/IP options and their sizes for Open Transport.
Hardware & Drivers 1999-04-26
Tips on USB driver matching for Mac OS X (HTML)
QA1076: Gives some tips on getting USB driver matching to work.
Hardware & Drivers 2008-08-14
Use the Doorbell (HTML) (日本語 HTML)
Deprecated - FW01: Explains the function of the FireWire Serial Bus Protocol 2 (SBP2) doorbell.
Hardware & Drivers 1999-05-17
Using "words" in Open Firmware (HTML)
HW73: Explains how to search for specific entries within all the global and local Open Firmware words.
Hardware & Drivers 1999-10-11
Video capture with multiple IIDC cameras (HTML)
QA1365: Discusses factors which influence the number of IIDC cameras that can simultaniously be used for capture.
Hardware & Drivers 2008-08-08
Was that a path I just saw? (HTML)
HW101: Describes the Open Firmware path that is occasionally shown at boot time.
Hardware & Drivers 2000-10-06
What are configuration variables in Open Firmware? (HTML) (日本語 HTML)
HW38: Defines the configuration variables in Open Firmware.
Hardware & Drivers 1999-02-15
What are generic names in Open Firmware? (HTML) (日本語 HTML)
HW34: Documents the generic names in Open Firmware.
Hardware & Drivers 1999-02-15
What are snag keys in Open Firmware? (HTML) (日本語 HTML)
HW35: Explains Open Firmware snag keys, including examples of their function.
Hardware & Drivers 1999-02-15
What is a CardBus host bus adapter HBA? (HTML)
HW79: Explains what a CardBus host bus adapter (HBA) is and discusses its implementation on the Macintosh.
Hardware & Drivers 1999-11-15
What is a tokenizer? (HTML) (日本語 HTML)
HW58: Defines a tokenizer.
Hardware & Drivers 1999-03-29
What is an Open Firmware devalias? (HTML)
HW99: Describes devaliases in Open Firmware.
Hardware & Drivers 2000-10-06