The updated MacBook Pros released by Apple this week are performing in line with what you might expect, given the changes to the laptop line. But one puzzling result in a test we run to gauge graphics performance prevents us from making a definitive claim about the new MacBook Pros's performance just yet.

We got our hands on two 15-inch MacBook Pros -- the 2.2GHz configuration and the 2.4GHz offering -- nearly immediately after Apple's Tuesday announcement. Though outwardly identical to the previous generation of professional portable Macs, these updated models have undergone something of a major overhaul underneath the hood.

All MacBook Pros now ship with 2GB of 667MHz DDR2 SDRAM, up from the 1GB that was standard on all old models; memory capacity has been boosted to 4GB. The updated models also have a faster frontside bus running at 800MHz (up from 667MHz). They're the first Intel-based Mac laptops to feature nVidia graphics--specifically the GeForce 8600M GT graphics processor with either 128MB of dedicated video ram in the 2.2GHz model or 256MB in the 2.4GHz model.

A green screen

Another change to this generation of MacBook Pros is something that Steve Jobs hinted at in his open letter on Apple's environmental policies: LED-backlit screens. Featured in the 15-inch models, LED backlights can help improve battery life while being more environmentally friendly by eliminating the mercury found in the fluorescent lamps behind most LCD screens. (We haven't had a chance to measure the battery life impact just yet--those results will come later.)

So how do the other changes affect performance? As we've seen in previous testing, adding RAM doesn't always mean better benchmark scores, as most of our tests perform just fine with 1GB of RAM. We added 1 GB of RAM to all of the baseline systems to level the playing field. But our recent tests of the 2.16GHz black MacBook with its standard 1GB of RAM yielded an identical Speedmark score with or without the extra RAM.

The MacBook Pro processor speeds, now about 2- to 3-per cent faster, did show some improvement, with the 2.4GHz model beating out the older 2.33GHz MacBook Pro in just about every test, including Photoshop, Cinema4D and Compressor.

Unusual results

Then there's that puzzling result, which came in our 3-D game tests with Unreal Tournament 2004. The 2.4GHz MacBook Pro, powered by the nVidia graphics chip, posted 28 per cent slower frame rates than the 2.33GHz model with ATI graphics. Further testing involving other games indicated that Unreal Tournament was the exception to the rule -- the new 2.4GHz MacBook Pro beat out the 2.33GHz model by 28 percent in our Doom tests and 33 percent in Quake 4 frame rates. Even more impressive was the 2.4GHz's score versus the standard 2.66GHz Quad-core Mac Pro--the systems were in a virtual dead heat in both Quake and Doom tests.

All systems were running Mac OS X 10.4.9 with 2GB of RAM. We used Unreal Tournament 2004's Antalus Botmatch average-frames-per-second score; we tested at a resolution of 1,024-x-768 pixels at the Maximum setting with both audio and graphics enabled. Doom 3 was set to use ultra high video setting, 1024 x 768 resolution, V-sync No, Antialiasing Off and all other settings set to Yes. Quake 4 was set to 1024 x 768 resolution, high quality video, full screen, multiprocessor on, V-sync No, antialias Off and all other advanced settings set to Yes.

The Unreal Tournament test result factors into a system's overall Speedmark score, and the new MacBook Pro's unexplained slow frame rates are dragging those Speedmark scores down. We've contacted MacSoft and Apple, and they are looking into the problem. Until we figure out the reason for the Unreal Tournament results, we'll wait to publish a Speedmark score.

Look for our full review soon.

(Testing was carried out James Galbraith, Brian Chen, and Jerry Jung at Macworld Labs).