Overview to the eMac
This chapter lists the features of the eMac and provides information about a few software issues of interest to developers.
In this section:
New Features
All Features
External Features
System Software
New Features
The features that have changed 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 GHz. For more information, see “PowerPC G4 Microprocessor.”
Hard disk storage: The built-in hard disk drive has a capacity of 40 GB or 80 GB. Some configurations have 80 GB and 160 GB build-to-order options. For more information, see “Hard Disk Drive.”
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 GHz. For more information, see “PowerPC G4 Microprocessor.”
Main memory bus: The speed of the memory bus is 133 MHz. For more information, see “Main Memory Bus.”
Cache: The 256 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 eMac comes with 128 or 256 MB of PC133 SDRAM installed in one of two standard 168-pin DIMM expansion slots. The RAM slots can support up to 512 MB each for a maximum total of 1 GB. For more information, see “RAM Expansion Modules.”
Hard disk storage: The built-in hard disk drive has a capacity of 40 GB or 80 GB. Some configurations have 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 DVD-ROM/CD-RW drive: One configuration has a combination DVD-ROM/CD-RW drive. For more information, see “Combo Drive DVD-ROM/CD-RW.”
SuperDrive (CD-RW/DVD-R): One configuration has a SuperDrive (CD-RW/DVD-R). For more information, see “SuperDrive DVD-R/CD-RW Drive.”
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 Radeon 7500 IC with 32 MB 180 MHz DDR memory. For more information, see “Video Display Subsystem.”
Video RAM: The video hardware includes 32 MB of DDR video memory, which 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 1.1 ports on the main chassis and two more on the keyboard. For more information, in “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 V.92 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-TX 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.”
Sound: 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 “Sound 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 40.7 cm (15.9 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, below the display, the following features:
Center-positioned, tray-loading CD-ROM, Combo drive, or SuperDrive
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 ports
Video monitor connector (mini-VGA)
Headphone jack
Sound-in jack
The receptacle for the power cord is located on the back. The back 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 10.3 or later installed as the default system. Mac OS 9 applications can be run in Classic mode. 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 PowerMac4,4.
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 “bootargs” property of the “chosen” node 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" |
Once the DB_NMI bit is set, reboot the machine by pressing the power button for approximately 3 seconds, thus generating an NMI.
Note: If the power button is pressed for more than five seconds, the system will immediately power off.
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.
% sudo nvram boot-args="" |
Note: The debug flags bit will be cleared if you use System Preferences to change the startup disk. It may also be cleared if you perform an installation that requires a restart.
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:
http://developer.apple.com/hardwaredrivers/ve/index.html
© 2001, 2003 Apple Computer, Inc. All Rights Reserved. (Last updated: 2003-11-20)