iMac’s new RAGE 128 Ultra graphics chip revealed

Flower Power and Blue Dalmatian designs aside, Apple’s new iMac models feature some important changes under the hood, such as the inclusion of video mirroring capability, AirPort support and FireWire across the entire product spectrum, rather than just on select models. Apple’s midrange and Special Edition iMac models also get another change in the form of a new video processor, the RAGE 128 Ultra.

Apple’s recent relationship with graphics chip maker Nvidia has yielded results in the form of new video cards and video options for the Power Mac G4 line, but the iMac line continues to depend on graphics hardware developed by ATI. In fact, ATI remains standard issue across most of Apple’s product lines, with its chips and graphics cards used in iMacs, iBooks and the PowerBook G4. ATI has been a chip provider to Apple for several years — its Radeon products are also available for the Mac both as retail products and as factory-installed OEM choices on Power Mac G4s and the G4 Cube.

ATI’s RAGE 128 Pro graphics subsystem has been standard issue on iMacs for some time now, but according to the specifications posted to Apple’s Web site, the heretofore standard RAGE 128 Pro configuration with 8MB of SDRAM is now limited to the lower-priced 400 MHz iMac model. The new midrange 500 MHz systems and the 600 MHz Special Edition iMac models now feature the RAGE 128 Ultra chipset with 16MB of SDRAM on board.

To find out more about this new chipset, MacCentral went straight to the horse’s mouth and talked with ATI Technologies Inc.

ATI Mac product manager Stephanie Castura confirms that the RAGE 128 Ultra model is now in production. According to Castura, the new RAGE 128 Ultra is functionally identical to the RAGE 128 Pro chip it replaces.

“The RAGE 128 Ultra is a cost-reduced version of the very popular Rage 128 Pro,” said Castura. “It has a new process and broader memory support. Because they are virtually the same chip, ATI made a silent transition from the 128 Pro to the Ultra.”

The key difference that iMac watchers may want to note is not the chip itself, but the configuration it’s available in — the 500MHz and 600MHz now ship with 16 MB of SDRAM, twice as much video RAM as what’s available in the low-end 400 MHz system, and twice as much as what was available in the previous generation of iMac as well. The extra RAM may provide some performance benefit for graphically intensive programs that need the extra space in video memory to buffer frame information quickly.