The next version of Adobe's collection of pro-level design tools, Creative Suite 4, will be the first to be available as a 64-bit version - though initially only for the 64-bit version of Windows Vista.

Mac users have to wait for 64-bit versions of some applications, including Photoshop – with Adobe blaming the delay on having to move to the Carbon development language.

This is because many of the applications which make up the current Creative Suite (including Photoshop) are written in the Carbon development language rather than Cocoa. When at WWDC 2007 Apple revealed that it would not support 64-bit in Carbon, Adobe realized it would need to rewrite some of its applications in Cocoa, Apple's collection of frameworks, APIs, and accompanying runtimes that make up the development layer of Mac OS X, before the applications would be able to take advantage of 64-bit computing power.

"We have to rewrite from scratch," said Adobe Photoshop product manager John Nack. "This makes the cost of the move considerably greater than for Windows. So we will ship 64-bit Windows version first," he added.

32-bit operating systems such as the standard versions of Windows XP and Vista, and Mac OS X 10.4 can utilize up to 4GB of RAM (though on Windows this is limited to 3GB for technical reasons). 64-bit versions of Windows and Mac OS X 10.5 can access much more – up to a theoretical limit of over 17 billion GB.

The 32-bit versions of Adobe's applications can access up to 2GB of RAM each, though many include tricks to use more. Photoshop let's plug-ins access higher areas of memory, while After Effects can split its rendering into different processes for each chip core in its host computer – which can each access up to 2GB of its own.

Cooking with Cocoa

When Carbon-64 was cancelled Adobe "took resources from the CS4 effort" to focus on the switch to Cocoa. "But we didn't think we should sacrifice the whole CS4 feature set for 64-bit on the Mac," revealed Nack.

Luckily the company wrote its relatively new Lightroom application in Cocoa so the transition to 64-bit can be immediate in that case, which is why the company introduced a 64-bit beta version of Lightroom to Mac users this morning.

When asked whether Adobe should have recognized the transition to Cocoa from Carbon sooner, Nack explained that while some might think that if software wants to be taken seriously as a Mac application it should be written in Cocoa, but "Apple's Finder is written in Carbon."

Nack would reveal no details of a shipping date for the new version of Creative Suite, saying that: "There is no time scale for CS4," and that it is: "Too early to say when we can deliver 64-bit for Mac."

He added that the next version of Photoshop will ship in 32- and 64-bit versions for Windows, with a simultaneous release of the software for the Mac, though the 64-bit version for Mac will be a subsequent release.

64-bit benefits for all?

The delay may not matter too much. Nack doesn't appear convinced that being able to exploit 64-bit computing immediately would be a great benefit to all Photoshop users.

"The real strength of 64-bit's is letting you address a large amount of memory. You'll see the biggest difference when working with large images or moving around a lot of data," he explained. To take advantage of 64-bit you need "more than 4GB Ram allocated to Photoshop," he added.

"If you are a Web user moving files around then you won't see much difference. Where you will see a substantial performance increase is with large files -- for example it could cut the time it takes to open a large image from 200 to 70 seconds.

"For pros it matters, for normal people it is more of a marginal performance difference.

"We don't want to overhype 64-bit with expectations that aren't going to be matched," he added.

But regardless of the status of 64-bit right now, Nack believes that getting set-up with 64-bit now is good because it will future-proof the Creative Suite applications for a time when all PCs and Macs support 64-bit and feature adequate RAM as standard.