Apple iMac - Manual (Page 25)

C H A P T E R 2
Architecture
Main Logic Board 25
■ the built-in modem
■ the infrared link
■ the Ethernet port
■ the sound ASIC
■ the internal IDE hard drive
■ the internal CD-ROM drive
■ the power manager IC
The Paddington IC is similar to the Heathrow IC used in the Power Macintosh
G3 computers and Macintosh PowerBook G3 computers. The main difference is
that the Paddington IC supports 100Base-TX Ethernet as well as 10Base-T.
USB Controller 2
The USB controller is a standard IC with two USB connectors. The register set
complies with the Open Host Controller Interface (OHCI) specification.
Video Display Subsystem 2
The display subsystem consists of a graphics controller ASIC, 2 MB of SGRAM
on the main logic board, and a connector for an additional 2 MB or 4 MB of
SGRAM on an SO-DIMM. For information about the SGRAM SO-DIMM, see
Chapter 4, “Expansion.”
The graphics controller IC is an ATI Rage IIc. It contains 2D and 3D acceleration
engines, a digital video port, front-end and back-end scalers, a CRT controller,
and a PCI bus interface with bus master capability.
For information about the display and supported resolutions, see Chapter 3,
“Devices and Ports.”
Built-in Modem 2
The built-in hardware modem is a separate module that is connected to the SCC
port A of the Paddington IC. The module contains a modem controller IC, a
datapump, and the interface to the telephone line (DAA).