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Overview to the eMac
This chapter lists the features of the eMac and provides information about a few software issues of interest to developers.
New Features
The features that have changed from the previous eMac are listed here with links to the sections that describe them.
Microprocessor: The eMac has a PowerPC G4 microprocessor running at a clock speed of 1.25 GHz or 1.42 GHz. For more information, see PowerPC G4 Microprocessor.
Memory: The computer comes with 256 MB or 512 MB of DDR333 (PC2700) SDRAM installed in an internal 184-pin DIMM expansion slot; 512 MB and 1 GB memory is available as a build-to-order option. The second user-accessible slot accepts a DIMM up to 512 MB. The maximum supported memory is 1 GB. For more information, see RAM Expansion Modules.
Graphics acceleration: The video circuits provide built-in 2D and 3D acceleration using an ATI Radeon 9200 with 32 MB DDR memory or an ATI Radeon 9600 with 64 MB DDR memory. For more information, see Video Display Subsystem.
SuperDrive (DVD+R DL/DVD±RW/CD-RW): One configuration has an 8x SuperDrive, which supports DVR+R Double Layer (DL) format. For more information, see SuperDrive.
Bluetooth Fully-integrated Bluetooth is available as a build-to-order option to enable short-range wireless connections between desktop and laptop computers and a host of other peripheral devices. For more information, see Bluetooth Technology.
All Features
Here is a complete list of the features of the eMac. Each feature is described in more detail in a later section.
Microprocessor: The eMac has a PowerPC G4 microprocessor running at a clock speed of 1.25 GHz or 1.42 GHz. For more information, see PowerPC G4 Microprocessor.
Main memory bus: The speed of the memory bus is 167 MHz. For more information, see Main ICs and Buses.
Cache: The 512 KB backside L2 cache is included on the microprocessor IC and has the same clock speed as the microprocessor. For more information, see Level 2 Cache.
Memory: The computer comes with 256 MB or 512 MB of DDR333 (PC2700) SDRAM installed in an internal 184-pin DIMM expansion slot; 512 MB and 1 GB memory is available as a build-to-order option. The second user-accessible slot accepts a DIMM with up to 512 MB. The maximum supported memory is 1 GB. For more information, see RAM Expansion Modules.
Hard disk storage: The built-in hard disk drive has a capacity of 5400 rpm 40 GB or 7200 rpm 80 GB. Some configurations have 7200 rpm 80 GB and 160 GB build-to-order options. For more information, see Hard Disk Drive.
CD-ROM drive: One configuration has a CD-ROM drive. For more information, see CD-ROM Drive.
Combo drive: One configuration has a combination DVD-ROM/CD-RW drive. For more information, see Combo Drive.
SuperDrive (DVD+R DL/DVD±RW/CD-RW): One configuration has an 8x SuperDrive, which supports DVR+R Double Layer (DL) format. For more information, see SuperDrive.
External video monitor: The mini-VGA display connector supports VGA, composite, and S-video formats for devices such as monitors, projectors, and television sets. A video adapter with composite and S-video connectors is available separately. For more information, see External Display Port.
Graphics acceleration: The video circuits provide built-in 2D and 3D acceleration using an ATI Radeon 9200 with 32 MB DDR memory or an ATI Radeon 9600 with 64 MB DDR memory. For more information, see Video Display Subsystem.
Video RAM: The video hardware supports 3D features and millions of colors in all resolutions. For more information, see Video Display Subsystem and Video Display.
USB ports: The eMac has three USB 2.0 ports on the main chassis. For more information, see USB Ports.
FireWire 400 ports: The eMac has two IEEE-1394a FireWire 400 ports, which support transfer rates of 100, 200, and 400 Mbps. For more information, see FireWire 400 Ports.
Target Disk Mode: The computer can act like a FireWire storage device connected to another computer. See Target Disk Mode.
Modem: Some models have a built-in fax modem with a 56 Kbps data rate. For more information, see Internal Modem.
Ethernet: The eMac has a built-in Ethernet port for a 10Base-T and 100Base-T operation. For more information, see Ethernet Port.
AirPort Extreme Card: An internal AirPort Extreme Card wireless LAN module is available as a build-to-order option or as a user-installable upgrade. For more information, see AirPort Extreme Card.
Bluetooth: Fully-integrated Bluetooth is available as a build-to-order option to enable short-range wireless connections between desktop and laptop computers and a host of other peripheral devices. For more information, see Bluetooth Technology.
Audio: The eMac has a built-in microphone, stereo speakers with amp, a line-level stereo input jack, and a stereo headphone jack. For more information, see Audio System.
Keyboard: The eMac comes with an Apple Keyboard. The keyboard is also a USB hub with two USB ports. For more information, see Keyboard.
Mouse: The computer comes with an Apple Mouse, a USB mouse with optical tracking. For more information, see Mouse.
Size and weight: The eMac is 40.6 cm (15.8 inches) high, 40.6 cm (15.8 inches) wide, and 43.3 cm (17.1 inches) deep; it weighs 22.7 kg (50.0 pounds).
Display: The eMac has a built-in 17-inch flat color CRT monitor with a 16-inch viewable diagonal. For more information, see Video Display.
External Features
The eMac is housed in a polycarbonate plastic enclosure that includes the display. The separate keyboard and mouse are also designed in polycarbonate plastic.
The front of the enclosure is dominated by the 17 inch flat display. The front also includes the following features:
Center-positioned, tray-loading CD-ROM, Combo drive, or SuperDrive (and no-optical drive configuration)
Access to AirPort Extreme Card slot
Stereo speakers, one on either side
Power-on light, located near the speaker on the right side; the light has a steady white glow when on; it pulses in sleep mode
Built-in microphone
The right side of the enclosure, as viewed from the front, contains the I/O panel. The I/O panel contains the following features:
Two FireWire 400 ports
Modem connector (on the models that have an internal modem)
Ethernet port
Three USB 2.0 ports
Video monitor connector (mini-VGA)
Headphone jack
Audio line-in port
The receptacle for the power cord is located on the right rear panel. The right rear panel also includes the following features:
Power button
Kensington security slot
The back portion of the bottom of the enclosure has a door that can be opened for access to the expansion RAM. For more information, see RAM Expansion Slots.
System Software
The eMac comes with Mac OS X version 10.4 installed as the default system. Mac OS 9 applications can be run in Classic mode. Install the Classic environment from the optical media shipped with your computer. For more information about Mac OS X, see the reference listed in Mac OS X.
Computer Identification
Rather than reading the box flag or the model string and then making assumptions about the computer’s features, applications that need to find out the features of the computer should use IORegistry calls to test for the features they require. IORegistry calls are part of the I/O Kit API. For more information, see the references listed at I/O Kit.
Asset management software that reports the kind of computer it is run on can obtain the value of the model property from the IOService plane of the IORegistry. For the eMac, the value of the string in the compatible property is PowerMac6,4.
NMI without Programmer’s Switch
Current Macintosh computers do not have a programmer’s switch, which allowed users to generate a non-maskable interrupt (NMI). The paragraphs below describe how to generate an NMI from a remote session for systems that do not have a physical programmer's switch.
Starting with Mac OS X 10.1.2, the OS will promote and recognize the DB_NMI bit in the debug parameter of the “boot-args” property from Open Firmware. When the DB_NMI bit is set, the user can generate a non-maskable interrupt (NMI) by pressing the system's power button. This replaces the power button’s sleep or wake response. The system reads the state of the bit at boot time from the boot-args configuration variable. For more information about the debug flags, please see Inside Mac OS X: Kernel Programming.
To set the DB_NMI bit, enter the following command at the Terminal to display the current debug flag settings.
% nvram boot-args |
Add the parameter debug=0x4, as follows.
% sudo nvram boot-args="<current settings> debug=0x4" |
After the DB_NMI bit in the debug parameter is set, reboot the machine. After reboot, pressing the power button for approximately 1 second will generate an NMI.
The power button will retain this functionality until Mac OS X is restarted without the DB_NMI bit set. To clear this bit, issue the nvram command omitting debug=0x4 parameter, as follows, then restart the machine.
% sudo nvram boot-args="" |
Velocity Engine Acceleration
The Velocity Engine (an implementation of AltiVec) is the vector processing unit in the PowerPC G4 microprocessor. Some system software has been modified to take advantage of the accelerated processing that the Velocity Engine makes possible. System software has also been modified to support low-level operations using the Velocity Engine.
For complete information on the Velocity Engine, refer to the following Apple website:
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