Apple’s new education-only eMac system grabbed the lion’s share of public attention when it was unveiled on Monday, but another significant announcement was made. Apple also introduced a new
PowerBook G4 top-end model, with several enhancements including a new video subsystem. To find out more about the new PowerBook’s graphics capabilities, MacCentral talked with the company that makes the graphics hardware,
ATI Technologies Inc.
In addition to a faster processor and a 15.2-inch LCD screen with a higher native resolution than previous models, the new 800MHz PowerBook G4 also sports a Mobility Radeon 7500 graphics processor — a faster processor that’s considerably more capable than its predecessor, the Radeon Mobility. ATI Mobile Business Unit group products manager David Cummings recently spoke to MacCentral about the new hardware in-depth to give us a better understanding of what it can really do.
DVI now supported on PowerBook G4s
The most obvious outward difference between this chip and previous models is the PowerBook G4’s newfound support for the Digital Visual Interface, or DVI. Previous models have sported analog VGA and S-video connections, but the new 800MHz PowerBook G4 is the first Mac laptop to sport an external digital video connector.
DVI has long been standard-issue on digital flat-panel displays, which means that the new PowerBook can now attach to a variety of displays available from third parties. Ironically, Apple’s insistence at using the ADC (Apple Display Connector) on its own line of flat-panel displays demands that owners of the new PowerBook G4 purchase an adapter in order to get the displays to work with the new PowerBook.
Cummings explained that external support for a DVI connector is no small feat. It’s something that very few PC-based notebook computers have outside of bulky external docking stations.
“Internally, the Mobility Radeon 7500 utilizes a TMDS transmitter that makes it possible for the DVI interface to work,” said Cummings. “It works in the same way we provide all the functionality for the PowerBook G4’s own LCD to work.”
3D gets a huge boost
The Mobility Radeon 7500 is also distinctly faster for 3D work than its predecessor. This is the first ATI graphics processor to be installed on a PowerBook model that features hardware-based transform and lighting (T&L) capabilities. Such functionality promises almost twice the performance power when it comes to running sophisticated software that depends on 3D rendering that heavily depends on geometric calculation.
Hardware T&L has another benefit: the new PowerBook G4 is the best Apple laptop yet for playing 3D games. Apple has benched the new system running Id Software’s popular 3D action game Quake III Arena at 68 frames per second. That’s a direct result of the Mobility Radeon 7500’s architecture, said Cummings. He added that Apple’s Quake III Arena benchmark is more than 80 percent faster than the previous top-end PowerBook.
If you like to use your PowerBook to watch DVD movies, Cummings said the Mobility Radeon 7500 comes in handy there, too. Cummings said that the chip decodes MPEG2 video at full frame rates for silky-smooth playback of DVD video.
Architectural improvements abound
Other changes under the hood include the Mobility Radeon 7500’s memory architecture. The memory interface is twice the size as the previous generation — 128 bit versus 64 bit — and twice the amount of RAM — 32MB of Double Data Rate (DDR) RAM, as opposed to 16MB with the older Mobility Radeon.
The Mobility Radeon 7500 runs faster, too — the chip operates at a core clock speed of 230MHz, while its predecessor clocked at 166MHz.
Not much of a power penalty
Despite this new power and sophistication, Cummings claimed that the Mobility Radeon 7500 sports “only marginally higher” power requirements than the Mobility Radeon. “[Power consumption] is a big focus area for our engineering team,” said Cummings.
The Mobility Radeon 7500’s power conservation is the result of some sophisticated power management technology that’s built into the chip, according to Cummings. The chip utilizes dynamic clock gating, for example.
“It powers down components or blocks within the accelerator that aren’t being used,” explained Cummings. “Say you’re running a DVD, for example. There’s no need to power the 3D accelerator, so the chip can cut power to that component.”
Cummings also said that the Mobility Radeon 7500 could dynamically adjust its own clock speed, which also helps to conserve power. “If the highest clock speed isn’t necessary for the given task, the chip will run slower,” he said.
Comparable to desktop model
Cummings said that the Mobility Radeon 7500 is very comparable to its desktop counterpart, which is available as a configure-to-order option on Power Mac G4 models. Thermal and power considerations germane to laptop configurations demand some compromises like a lower clock speed, of course, but that’s about it.
“The Mobility Radeon 7500 is really a superset of what’s available on desktop models,” said Cummings. “We take the same core technology and add mobile features.”