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Input and Output Devices
This chapter describes the PowerMac G4 computer’s built-in I/O devices and the ports for connecting external I/O devices. Each of the following sections describes an I/O port or device.
USB Ports
The PowerMac G4 computer has two external Universal Serial Bus (USB) ports on the back and two on the keyboard. The USB ports are used for connecting the keyboard and mouse as well as additional I/O devices such as printers, scanners, and low-speed storage devices. The USB ports are off of the USB controller connected to the PCI bus.
Each USB port is connected to a separate USB root hub, allowing both USB ports to support 12 Mbps devices at the same time with no degradation of their performance. The USB root hubs also connect to the internal USB modem and Bluetooth modules and to the USB port on the ADC monitor connector.
The USB ports comply with the Universal Serial Bus Specification 1.1 Final Draft Revision. The USB register set complies with the Open Host Controller Interface (OHCI) specification.
For more information about USB on Macintosh computers, please refer to Apple Computer’s Mac OS USB DDK API Reference and the other sources listed in USB Interface.
USB Connectors
The USB ports use USB Type A connectors, which have four pins each. Two of the pins are used for power and two for data. Figure 3-1 shows the connector and Table 3-1 shows the signals and pin assignments.
Pin | Signal name | Description |
|---|---|---|
1 | VCC | +5 VDC |
2 | D– | Data – |
3 | D+ | Data + |
4 | GND | Ground |
The PowerMac G4 computer provides power for the USB ports at 5 V and up to 500 mA on each port. The ports share the same power supply; a short circuit on one disables both ports until the short has been removed.
The USB ports support both low-speed and high-speed data transfers, at 1.5 Mbits per second and 12 Mbits per second, respectively. High-speed operation requires the use of shielded cables.
The Macintosh system software supports all four data transfer types defined in the USB specification.
Waking Up From Sleep
As defined in the USB-suspend mode of the USB specification, USB devices can provide a remote wakeup function for the computer. The USB root hub in the computer is set to support remote wakeup whenever a device is attached to the bus. The device wakes the computer by sending a Resume event to the USB root hub. The mouse and keyboard that come with the computer use this method to wake the computer on a key press or mouse click.
FireWire Ports
The PowerMac G4 computer has one FireWire 800 IEEE 1394b port and two FireWire 400 IEEE 1394a ports. Each FireWire port
supports booting the system from a mass storage device
supports target disk mode
provides bus repeating capability as long as the computer is connected to AC power
The three FireWire ports share a single power supply that can provide up to 15 watts total. The three ports are all on the same FireWire bus and can connect to up 62 other FireWire devices.
The FireWire hardware and software provided with the PowerMac G4 computer are capable of all asynchronous and isochronous transfers defined by IEEE standard 1394a and 1394b.
Developers of FireWire peripherals are required to provide device drivers. A driver for DV (digital video) is included in QuickTime 4.0 and later versions.
For more information about FireWire on Macintosh computers, please refer to the Apple FireWire website and the other sources listed in FireWire Interface.
FireWire 800 Connector
The FireWire 800 port on the PowerMac G4 computer is based on IEEE 1394b and enables a 800 Mbps transfer rate. FireWire 800 uses a 9-pin connector and is backwards compatible with original 1394 FireWire devices with 6-pin or 4-pin connectors. With the appropriate cable, the 9-pin port works seamlessly with legacy FireWire devices. Cables are available to go from both 6-pin and 4-pin connectors to a 9-pin, and 9-pin to 9-pin.
The 9-pin FireWire 800 connector is shown in Figure 3-2. Its connector signals and pin assignments are shown in Table 3-2.
Pin | Signal name | Description |
|---|---|---|
1 | TPB– | Twisted-pair B Minus |
2 | TPB+ | Twisted-pair B Plus |
3 | TPA– | Twisted-pair A Minus |
4 | TPA+ | Twisted-pair A Plus |
5 | TPA (R) | Twisted-pair A Ground Reference |
6 | VG | Power Ground |
7 | SC | Status Contact (no connection; reserved) |
8 | VP | Power Voltage (approximately 25 V DC) |
9 | TPB (R) | Twisted-pair B Ground Reference |
VP (pin 8) provides up to 15 W power, shared with the other FireWire connectors. The voltage on the power pin is approximately 25 V.
The 9-pin FireWire port is capable of operating at 100, 200, 400, and 800 Mbps, depending on the device it is connected to. Using a cable with a 9-pin connector at one end and a 4-pin or 6-pin connector at the other, the 9-pin port is capable of directly connecting to all existing FireWire devices. Using a cable with 9-pin connectors at both ends, the 9-pin port is capable of operating at 800 Mbps.
The IEEE 1394b standard defines long-haul media using Cat 5 UTP and several kinds of optical fiber. The PowerMac G4 computer is interoperable with such cables but cannot be directly connected to them. To use long-haul cables, connect the computer to a 1394b hub that has the desired kind of long-haul connectors. If the hub has a bilingual port, that port can be connected to any of the computer’s FireWire ports. If the hub has a beta-only port, it can be connected only to the computer’s 9-pin port.
FireWire 400 Connector
The FireWire 400 ports 1 and 2 use the six-pin connectors shown in Figure 3-3. The connector signals and pin assignments are shown in Table 3-3.
Pin | Signal name | Description |
|---|---|---|
1 | Power | Power (approximately 25 V DC) |
2 | Ground | Ground return for power and inner cable shield |
3 | TPB– | Twisted-pair B Minus |
4 | TPB+ | Twisted-pair B Plus |
5 | TPA– | Twisted-pair A Minus |
6 | TPA+ | Twisted-pair A Plus |
Shell | — | Outer cable shield |
The power pin provides up to 15 W total power, shared with the other FireWire connectors. The voltage on the power pin is approximately 25 V.
Pin 2 of the 6-pin FireWire connector is ground return for both power and the inner cable shield. In a FireWire cable with a 4-pin connector on the other end, the wire from pin 2 is connected to the shell of the 4-pin connector.
The signal pairs are crossed in the cable itself so that pins 5 and 6 at one end of the cable connect with pins 3 and 4 at the other end. When transmitting, pins 3 and 4 carry data and pins 5 and 6 carry clock; when receiving, the reverse is true.
Booting from a FireWire Device
The PowerMac G4 computer can boot from a FireWire storage device that implements SBP-2 (Serial Bus Protocol) with the RBC (reduced block commands) command set. Detailed information is available from Developer Technical Support at dts@apple.com.
For additional information about the FireWire interface and the Apple API for FireWire device control, see the references shown in FireWire Interface.
Target Disk Mode
The user has the option at boot time to put the computer into a mode of operation called Target Disk Mode (TDM). When the PowerMac G4 computer is in Target Disk Mode and connected to another Macintosh computer by a FireWire cable, the PowerMac G4 computer operates like a FireWire mass storage device with the SBP-2 (Serial Bus Protocol) standard. Target Disk Mode has two primary uses:
high-speed data transfer between computers
diagnosis and repair of a corrupted internal hard drive
The PowerMac G4 computer can operate in Target Disk Mode as long as the other computer has a 1394a or 1394b FireWire port and either any version of Mac OS X or Mac OS 9 with FireWire software version 2.3.3 or later.
To put the PowerMac G4 computer into Target Disk Mode, restart the computer and hold down the T key until the FireWire icon appears on the display. Then connect a FireWire cable from the PowerMac G4 to the other computer. When the other computer completes the FireWire connection, a hard disk icon appears on its desktop.
If you disconnect the FireWire cable or turn off the PowerMac G4 computer while in Target Disk Mode, an alert appears on the other computer.
To take the PowerMac G4 out of Target Disk Mode, drag the hard disk icon on the other computer to the trash, then press the power button on the PowerMac G4 computer.
Ethernet Port
The PowerMac G4 computer has a built-in Ethernet port that supports 10Base-T, 100Base-T, and 1000Base-T Gigabit transfer rates. In operation, the actual speed of the link is auto-negotiated between the computer’s PHY device and the hub, switch, or router to which it is connected. The Ethernet port is auto-sensing and self-configuring to allow connection via either a cross-over or straight-through cable.
Both CAT 5 unshielded twisted pair (UTP) and shielded twisted pair (STP) cables work with the Ethernet port. An STP cable is recommended for noisy environments or run of greater than 100 meters.
The connector for the Ethernet port is an RJ-45 connector on the back of the computer. Table 3-4 shows the signals and pin assignments for 10Base-T and 100Base-T operation. Table 3-5 shows the signals and pin assignments for 1000Base-T operation.
Pin | Signal name | Signal definition |
|---|---|---|
1 | TXP | Transmit (positive lead) |
2 | TXN | Transmit (negative lead) |
3 | RXP | Receive (positive lead) |
4 | – | Not used |
5 | – | Not used |
6 | RXN | Receive (negative lead) |
7 | – | Not used |
8 | – | Not used |
Pin | Signal name | Signal definition |
|---|---|---|
1 | TRD+(0) | Transmit and receive data 0 (positive lead) |
2 | TRD–(0) | Transmit and receive data 0 (negative lead) |
3 | TRD+(1) | Transmit and receive data 1 (positive lead) |
4 | TRD+(2) | Transmit and receive data 2 (positive lead) |
5 | TRD–(2) | Transmit and receive data 2 (negative lead) |
6 | TRD–(1) | Transmit and receive data 1 (negative lead) |
7 | TRD+(3) | Transmit and receive data 3 (positive lead) |
8 | TRD–(3) | Transmit and receive data 3 (negative lead) |
To interconnect two computers for 1000Base-T operation, you must use 4-pair cable (Category 5 or 6).
The Ethernet interface in the PowerMac G4 computer conforms to the ISO/IEC 802.3 specification, where applicable, and complies with IEEE specifications 802.3i (10Base-T), 802.3u-1995 (100Base-T), and 802.3ab (1000Base-T).
Disk Drives
The PowerMac G4 computer has two 5.25 inch bays for optical drive access through the front panel and four 3.5 inch bays for internal hard disk drives, two in the front and two in the back. The optical drives are on the EIDE data bus.
The PowerMac G4 computer supports ATA and ATAPI internal storage devices that are set for cable select mode, which force the devices to set their IDs based cable position. When transferring a drive to the PowerMac G4 from older computers, be sure to set the cable select on the drive. For additional information on cable select, refer to the following website.
http://www.seagate.com/support/kb/disc/faq/ata_cable_select.html
Hard Disk Drives
The enclosure has two drive carriers, each with two 3.5 inch bays for fixed-media mass storage devices. The rear drive carrier includes data and power connectors for the boot drive and a second internal drive on the Ultra ATA/100 interface. The front drive carrier has data and power connectors for one or two additional drives on the Ultra ATA/66 interface. A drive in either of the internal carriers can also be connected to an optional PCI controller card.
The boot drive occupies one of the bays in the rear carrier and is connected by way of an Ultra ATA/100 (ATA-5) interface. The Ultra ATA/100 cable assembly also has data and power connectors for a second 3.5 x 1-inch drive in the rear carrier.
The drives on the Ultra ATA/100 bus operate in a Device 0/1 configuration. The boot drive is cable-selected as Device 0 (master). An additional Ultra ATA/100 is configured as Device 1 (slave).
Like the drives on the Ultra ATA/100 bus, the drives on the Ultra ATA/66 bus operate in a Device 0/1 configuration. The Ultra ATA/66 bus supports PIO Mode 4, DMA Mode 2, and Ultra DMA Mode 4 data transfers.
SCSI Drive
SCSI drives and SCSI PCI controller cards are available from third party providers. The PowerMac G4 computer supports one to four SCSI drives.
Optical Drives
The optical drives are connected by way of an EIDE (ATA-3) interface.
The two optical drives occupy both device locations on the IDE channel. The devices operate in an IDE Device 0/1 configuration. The upper optical drive is Device 0 (master) and the lower drive is Device 1 (slave). Power and data cables are provided for both bays even if only one bay is occupied.
The EIDE bus supports PIO Mode 4 and MultiWord DMA Mode 4 data transfers.
SuperDrive
Some configurations of the PowerMac G4 computer have a SuperDrive (combination DVD-R and CD-RW drive). The SuperDrive has a tray for loading the disc.
The SuperDrive can read and write DVD media and CD media, as shown in Table 3-6. The DVD-R/CD-RW drive also provides DVD-Video playback. (The G4 microprocessor provides the MPEG 2 decoding.)
Media type | Reading speed (maximum) | Writing speed |
|---|---|---|
DVD-R | 2x (CLV) | 4x/2x/1x (CLV) depending on media type — see text below table |
DVD-ROM | 8x (CAV max) | _ |
CD-R | 32x (CAV max) | 16x (CLV) |
CD-RW | 16x (CAV max) | 8x (CLV) high speed CD-RW disc |
CD or CD-ROM | 32x (CAV max) | – |
For the 4x SuperDrive, the media compares as follows.
the following qualified 4x media burns at up to 4x:
Maxell
MCC/Verbatim
Pioneer Video
Taiyo Yuden
TDK
MCI (Mitsui)
Fuji
the following qualified 2x media burns at up to 2x:
Maxell
MCC/Verbatim
Pioneer Video
Taiyo Yuden
TDK
Sony
burn speeds for other media may vary
For 2x SuperDrive, it is recommended to continue using 2x media.
The Apple SuperDrive writes to DVD-R 4.7 gigabyte General Use media. These discs are playable in most standard DVD players and computer DVD-ROM drives. For a list of players tested by Apple for playability, refer to
http://www.apple.com/dvd/compatibility/
For compatibility information regarding recordable DVD formats, refer to
http://dvddemystified.com/dvdfaq.html#4.3
Digital audio signals from the SuperDrive can be played through the sound outputs under the control of the Sound Manager.
The SuperDrive is an ATAPI drive and is cable-select enabled such that Device 0 master and Device 1 is slave.
Combo (DVD-ROM/CD-RW) Drive
Some configurations of the PowerMac G4 computer have a combination DVD-ROM and CD-RW drive. The drive has a tray for loading the disc.
The Combo drive can read DVD media and read and write CD media, as shown in Table 3-7. The DVD-ROM/CD-RW drive also provides DVD-Video playback. (The G4 microprocessor provides the MPEG 2 decoding.)
Media type | Reading speed | Writing speed |
|---|---|---|
DVD-R | 4x (CAV max) | – |
DVD-ROM | 12x (CAV max) | – |
CD-R | 32x (CAV max) | 32x (ZCLV) |
CD-RW | 20x (ZCAV max) | 10x (CLV, for high speed media) |
CD or CD-ROM | 32x (CAV max) | – |
Digital audio signals from the Combo drive can be played through the sound outputs under the control of the Sound Manager.
Internal Modem
The PowerMac G4 computer has an internal modem module. The external I/O connector for the modem is an RJ-11 connector installed on the rear panel of the computer. The modem has the following features:
modem bit rates up to 56 Kbps, supports K56flex modem standard and V.90 and V.92 for the Dash 2 modem
fax modem bit rates up to 14.4 Kbps
The modem appears to the system as a USB device that responds to the typical AT commands. The modem provides a sound output for monitoring the progress of the modem connection.
AirPort Extreme Card (Optional)
The PowerMac G4 computer supports the AirPort Extreme Card, an internal wireless LAN module. The AirPort Extreme Card is available as a build-to-order option or as a user-installable upgrade through the Apple Store.
By communicating wirelessly with a base station, the AirPort Extreme Card can be used for Internet access, email access, and file exchange. A base station provides the connection to the Internet or the bridge between the wireless signals and a wired LAN or both. The AirPort Extreme Base Station has connectors for a wired LAN, a DSL or cable modem, and a standard telephone line using the built-in 56 Kbps modem that is available on some base stations.
AirPort Extreme transmits and receives data at speeds up to 54 Mbps, comparable to wired networking speeds. Airport Extreme is also compatible with other devices that follow the IEEE 802.11b standard, including PC's. For more information about Wi-Fi and compatibility, see the reference at Wireless Networks.
Data Security
AirPort Extreme has several features designed to maintain the security of the user’s data:
The system uses direct-sequence spread-spectrum (DSSS) technology that uses a multibit spreading code that effectively scrambles the data for any receiver that lacks the corresponding code.
The system can use an Access Control List of authentic network client ID values (wireless and MAC Addresses) to verify each client’s identity before granting access to the network.
When communicating with a base station, AirPort Extreme uses up to 128-bit encryption to encode data while it is in transit.
The AirPort Extreme Base Station can be configured to use NAT (Network Address Translation), protecting data from would-be Internet hackers.
The AirPort Extreme Base Station can authenticate users by their unique Ethernet IDs, preventing unauthorized computers from logging into a network. Network administrators can take advantage of RADIUS compatibility, used for authenticating users over a remote server. Smaller networks can offer the same security using a local look-up table located within the base station.
As an additional data security measure, VPN can be used in conjunction with the AirPort Extreme data security.
AirPort Extreme Hardware
The AirPort Extreme Card is a wireless LAN module based on the IEEE draft specification of the 802.11g standard using both OFDM (orthogonal frequency-division multiplexing) and DSSS technologies. Using DSSS, AirPort Extreme is interoperable with PC-compatible wireless LANs that conform to the 802.11b standard at speeds of 11 Mbps, 5.5 Mbps, 2 Mbps, and 1 Mbps. Using OFDM, AirPort Extreme is compatible with all 802.11g draft standard speeds.
Two AirPort Extreme antennas are built into the computer’s enclosure. One antenna is always used for transmitting. Either of the two antennas may be used for receiving. Using a diversity technique, the AirPort Extreme Card selects the antenna that gives the best reception. AirPort Extreme shares the antennas with Bluetooth.
The AirPort Extreme wireless LAN is on the PCI bus.
AirPort Extreme Software
Software that is provided with the AirPort Extreme Card includes
AirPort Extreme Setup Assistant, an easy-to-use program that guides the user through the steps necessary to set up the AirPort Extreme Card or set up an AirPort Extreme Base Station.
Users can switch between wireless networks and can create and join peer-to-peer networks. These functions are accessed via the AirPort Extreme- Menu-Extra pulldown in System Preferences.
AirPort Extreme Admin Utility, a utility for advanced users and system administrators. With it the user can edit the administrative and advanced settings needed for some advanced configurations.
Bluetooth Technology (Optional)
Available as a fully integrated build-to-order option, Bluetooth is an open specification that enables short-range wireless connections between desktop and laptop computers and a host of other peripheral devices. Bluetooth support is built into Mac OS X and compliant with Bluetooth specification v1.1. It operates on a globally available 2.4 GHz frequency band (ISM band) for worldwide compatibility and has a maximum throughput of 1Mbps.
The Bluetooth technology supports the following profiles:
synchronization —enables synchronization of devices over Bluetooth
serial —provides a wireless serial connection to other Bluetooth devices
dial-up networking (DUN) — enables a mobile phone to act as a modem
object push —enables the transfer of files between Bluetooth devices
Bluetooth is available as a build-to-order option, which is installed by Apple at the time of purchase as a fully integrated module. Accessing the Bluetooth capabilities without purchasing the integrated module will require a third-party dongle.
For more information on Bluetooth technology, refer to Bluetooth.
Keyboard
The PowerMac G4 computer comes with a Apple Pro Keyboard. It is a full-size keyboard with function keys and separate keypad and editing sections.
The keyboard has an attached 1-meter cable and comes with a 1-meter extender cable for installations where the computer is located on the floor or away from the immediate desktop area.
Keyboard Features
Here is a list of the features of the Apple Pro Keyboard.
slope settable to either 0 or 6 degrees
108 keys (on the ANSI versions)
15 function keys
6 editing keys (Page Up, Page Down, Home, End, Forward Delete, and Help)
USB HID Consumer Page Usage multimedia control keys
full travel, standard pitch keys on alphanumeric, editing, and keypad sections, including function keys and cursor-position keys
localized worldwide: 33 versions, standard layouts (including: ANSI, JIS, ISO)
LED indicators in the Caps Lock and Num Lock keys
USB hub functionality with two USB sockets
Keyboard Layout
There are localized versions of the Apple Pro Keyboard for use in different parts of the world. The three standards used are ANSI (US and North America), JIS (Japan), and ISO (Europe).
Applications can determine which keyboard is connected by calling the Gestalt Manager and checking for the corresponding value of the gestaltKeyboardType selector:
gestaltUSBAndyANSIKbd(value = 204)gestaltUSBAndyISOKbd(value = 205)gestaltUSBAndyJISKbd(value = 206)
Figure 3-4 shows the keyboard layout for the ANSI keyboard.
MultiMedia Control Keys
The keyboard has six multimedia keys: Volume Up, Volume Down, Mute, Brightness Up (F15), Brightness Down (F14), and Eject. Theses keys provide direct control of the features on the computer by way of the USB.
If two removable media drives are installed, press Option-Eject to eject the disk on the second drive in the bottom drive bay.
Keyboard and USB
The Apple Pro Keyboard is designed to work with the computer by way of the USB ports. The keyboard has a captive cable with a USB Type A connector. The keyboard is a bus-powered USB hub with two USB Type A ports.
Apple provides a HID class driver for the Apple Pro Keyboard, which supports the USB boot protocol. Other keyboards intended for use on the Macintosh platform must support the HID boot protocol, as defined in the USB Device Class Definition for Human Interface Devices (HIDs).
Programmer’s Switches
Key combinations for programmer’s switches that used the Power button on earlier models now use the Eject key. Here are the key combinations for the PowerMac G4 computer.
Control-Command-Eject: restart immediately (reset)
Control-Command-Option-Eject: shut down immediately
Control-Eject: display the dialog for shutdown, restart, and sleep
The key combinations are decoded in software and may not be available under some crashed conditions.
Mouse
The PowerMac G4 computer comes with an Apple Pro Mouse. The mouse case is made of polycarbonate plastic like the computer.
The Apple Pro Mouse is a new design that uses optical tracking in place of the traditional rolling ball. It works on almost any surface, though nonreflective, opaque surfaces without repetitive patterns work best. In Mac OS X, the new Apple Pro Mouse resolution is switched to 800dpi and the xy displacement data are signed 16-bit values.
Sound System
Under the control of the system software, the sound circuitry can create and record sounds digitally. It can receive audio signals through the audio input jack and send audio signals to the internal speaker, the headphone jack, the audio output jack, and the Apple speaker minijack.
Audio signals from the audio input jack are converted to digital data internally. All audio is handled digitally inside the computer, including audio data from the CD or DVD drive and from devices connected to the USB and FireWire ports. Audio data is converted to analog form for output to the internal speaker, the headphone and line output jacks, and the Apple Pro Speaker minijack.
The sound circuitry handles audio data as 44.1 kHz, 16-bit samples. If audio data sampled at a lower rate on another computer is played as output, the Sound Manager transparently upsamples the data to 44.1 kHz prior to sending the audio data to the sound circuitry.
Plugging-in some components in the sound system mutes other components, as shown below:
When Plug-In: | This Is Muted: |
|---|---|
External speakers | Internal speakers |
Rear line-out | Internal and external speakers |
Front headphone | Internal and external speakers |
Audio Input Jack
The PowerMac G4 has a stereo audio line-in jack on the back panel. Low level consumer products operating below -10 dbu require a pre-amp.
The audio inputs are designed to accept high-level audio signals: 2 Vrms or +8 dbu, which is the standard output level from CD and DVD players. The output level of some consumer audio devices is lower, often 0.316 Vrms or –10 dbV. Sound recordings made on the PowerMac G4 with such low-level devices have more noise than those made with high-level devices. The user may obtain better results by connecting an amplifier between the low-level device and the computer’s audio input jack.
The audio input jack is a 3.5 mm miniature phone jack with the signals connected as follows:
Tip | Left-channel audio |
Ring | Right-channel audio |
Sleeve | Audio ground |
The sound input jack has the following electrical characteristics:
maximum input signal amplitude 2 Vrms (5.65 Vpp), +8 dbu peak
input impedance at least 47 kilohms
channel separation greater than 75 dB
recommended source impedance 2 kilohms or less
ground noise rejection greater than 75 dB
frequency response 20 Hz to 20 kHz, +0.5, –1.5 dB
distortion below –80 dB
signal to noise ratio (SNR) greater than 85 dB (unweighted)
Headphone Jack
The PowerMac G4 has a stereo headphone jack on the front of the enclosure. The headphone jack is suitable for connecting a pair of headphones or amplified external speakers. When a plug is inserted into the headphone jack, the internal speaker and the Apple Pro Speakers (if connected) are muted.
The sound input jack is a 3.5 mm miniature phone jack with the signals connected as follows:
Tip | Left-channel audio |
Ring | Right-channel audio |
Sleeve | Audio ground |
The headphone jack has the following electrical characteristics:
full-scale output level (open circuit) 1.5 Vrms (4.5 Vpp), +4 dbu peak
source impedance is 10 ohms
channel separation greater than 65 dB
recommended load impedance 32 ohms or greater
distortion, 32 ohm load, is better than –80 dB (0.01%)
frequency response, 32 ohm load, 20 Hz to 20 kHz, +0.5, –1.5 dB
signal-to-noise ratio (SNR) greater than 90 dB unweighted
Audio Output Jack
The PowerMac G4 has a stereo output jack on the back of the enclosure. The audio output jack is suitable for connecting amplified external speakers.
The audio output jack is a 3.5 mm miniature phone jack with the signals connected as follows:
Tip | Left-channel audio |
Ring | Right-channel audio |
Sleeve | Audio ground |
The audio output jack has the following electrical characteristics:
full-scale output level (open circuit) 1.5 Vrms (4.5 Vpp), +4 dbu peak
source impedance less than 10 ohms
channel separation greater than 70 dB
recommended load impedance 1 kilohm or greater
distortion is –80 dB (0.01%)
frequency response, with 10 kilohms load, 20 Hz to 20 kHz, +0.5, –1.5 dB
signal-to-noise ratio (SNR) greater than 90 dB
Apple Pro Speakers Minijack
The Apple Pro Speakers minijack is a stereo 2.5 mm miniature jack. It has a smaller diameter than the headphone jack so that the user cannot inadvertently plug headphones into it.
The electrical characteristics of the Apple Pro Speakers minijack are optimized for use with Apple Pro Speakers. The Apple Pro Speakers include an internal ROM that enables the computer to identify the speakers. Speakers other than the Apple Pro Speakers should not be connected to the Apple Pro Speakers minijack.
Video Monitor Ports
Depending on the configuration, the PowerMac G4 computer comes with either an ATI or an NVidia graphics card installed. The main features of the graphics cards are as follows:
Graphics IC | Video RAM | Connectors |
|---|---|---|
ATI Radeon 9000 Pro | 64 MB DDR | ADC and DVI |
NVidia GeForce4 MX | 64 MB DDR | ADC and DVI |
The NVidia GeForce4 Titanium 128 MB DDR, ADC/DVI graphics card and ATI Radeon 9700 Pro 128 MB DDR, ADC/DVI graphics card are available as build-to-order options.
All of the graphics cards support dual displays in either extended desktop or video mirroring mode.
The following sections describe the video connectors on the graphics cards.
Apple Display Connector
The graphics cards have an Apple proprietary connector called the ADC (Apple display connector). The connector carries both digital and analog video signals as well as USB and control signals and power for an external monitor. Figure 3-5 shows the contact configuration; Table 3-8 and Table 3-9 list the signals and pin assignments.
The maximum current available from the 25 V supply for the external monitor is 4.0 A.
Pin | Signal name | Pin | Signal name |
|---|---|---|---|
1 | 25 V Supply | 16 | TMDS Data1/3 Shield |
2 | 25 V Supply | 17 | TMDS Data3– |
3 | LED | 18 | TMDS Data3+ |
4 | TMDS Data0– | 19 | DDC CLock |
5 | TMDS Data0+ | 20 | Clock Return |
6 | TMDS Data0/5 Shield | 21 | USB Data+ |
7 | TMDS Data5– | 22 | USB Data– |
8 | TMDS Data5+ | 23 | USB Return |
9 | DDC Data | 24 | TMDS Data2– |
10 | Vsync | 25 | TMDS Data2+ |
11 | 25 V Return | 26 | TMDS Data2/4 Shield |
12 | 25 V Return | 27 | TMDS Data4– |
13 | Soft Power | 28 | TMDS Data4+ |
14 | TMDS Data1– | 29 | Clock+ |
15 | TMDS Data1+ | 30 | Clock– |
Pin | Signal name |
|---|---|
C1 | Analog Blue Video |
C2 | Analog Green Video |
C3 | Analog Horizontal Sync |
C4 | Analog Red Video |
C5 | Analog RGB Return and DDC Return |
The graphics data sent to the digital monitor use transition minimized differential signaling (TMDS). TMDS uses an encoding algorithm to convert bytes of graphics data into characters that are transition-minimized to reduce EMI with copper cables and DC-balanced for transmission over fiber optic cables. The TMDS algorithm also provides robust clock recovery for greater skew tolerance with longer cables or low-cost short cables. For additional information about TMDS, see the references shown in Digital Visual Interface.
DVI Connector
In addition to the ADC connector, both graphics cards also have a DVI connector. The DVI connector is a standard connector that carries only the digital video signals. Figure 3-6 shows the contact configuration; Table 3-10 lists the signals and pin assignments.
Pin | Signal name | Pin | Signal name |
|---|---|---|---|
1 | TMDS Data2– | 13 | TMDS Data3+ |
2 | TMDS Data2+ | 14 | +5V Power |
3 | TMDS Data2/4 Shield | 15 | Ground for +5V Power |
4 | TMDS Data4– | 16 | Hot Plug Detect |
5 | TMDS Data4+ | 17 | TMDS Data0– |
6 | DDC Clock | 18 | TMDS Data0+ |
7 | DDC Data | 19 | TMDS Data0/5 Shield |
8 | Analog vertical sync | 20 | TMDS Data5– |
9 | TMDS Data1– | 21 | TMDS Data5+ |
10 | TMDS Data1+ | 22 | TMDS Clock Shield |
11 | TMDS Data1/3 Shield | 23 | TMDS Clock+ |
12 | TMDS Data3– | 24 | TMDS Clock– |
C1 | Analog red | C4 | Analog horizontal sync |
C2 | Analog green | C5 | Analog ground (analog R, G, B return) |
C3 | Analog blue |
The graphics data sent to the digital monitor use transition minimized differential signaling (TMDS). TMDS uses an encoding algorithm to convert bytes of graphics data into characters that are transition-minimized to reduce EMI with copper cables and DC balanced for transmission over fiber optic cables. The TMDS algorithm also provides robust clock recovery for greater skew tolerance with longer cables or low-cost short cables.
For information about TMDS, see the reference listed in Digital Visual Interface.
Dual Display Extended and Mirror Modes
The PowerMac G4 is equipped with an ADC port for connecting an Apple display and a DVI port for a second digital display. Through these two ports, the PowerMac G4 supports dual displays in both extended desktop and video mirroring modes. Extended desktop mode lets users distribute work across two displays, increasing the amount of visible desktop space. Video mirroring mode displays the same information on both monitors, enabling the control of a presentation on one display, while allowing an audience to watch the presentation on a second display or projector. The PowerMac G4 can power two Apple Cinema HD Displays at a pixel resolution of 3800x1200.
To switch between extended desktop and video mirroring modes, open System Preferences, click Arrangement, and select or deselect the Mirror Displays option.
The scaling function is available when both monitors (main via ADC and second via DVI) are operating and the mirror mode is selected. However, the DVI monitor could have black borders during mirroring, depending on the supported timings between the two displays and on the monitor’s selection algorithm. Both displays show full-sized images only when the display resolution for the second monitor is set to the first display’s native resolution: 1920 by 1200. Both displays can operate with other resolution settings, but in mirror mode, one of them has a display that is smaller than the full screen and has a black border around it. With the resolution for the second monitor set to 640 by 480 or 800 by 600, the image on the first display is smaller than its screen. For resolution settings larger than 1280 by 854, the image on the second monitor is smaller than its screen.
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