Next Photoshop will get 64-bit boost--on Windows only

Adobe's forthcoming Photoshop CS4 will take the 64-bit plunge, improving performance and support for big files. But Mac users will have to wait until the CS4 successor.

Adobe Systems has shared the first scrap of information about its next version of Photoshop, CS4, and it's a doozy: there will be a 64-bit version of the photo-editing software, but only for Windows and not for Mac OS X.

Adobe generally keeps features in the Windows and Mac versions at a level of parity, but that wasn't possible this time around because of a change Apple made last year to the Mac's programming underpinnings, John Nack, Adobe's product manager for Photoshop, said in an interview.

"We're not going to ship 64-bit native for Mac with CS4," Nack said. "We respect Apple's need to balance their resources and make decisions right for that platform. But it does have an impact on developers."

(Read the "What derailed the 64-bit train?" section below if you want more details on why Adobe concluded it had to change plans.)

What does 64 bits get you, anyway? Chiefly, an easier way for a processor and software to use more than 4GB of memory. In addition, the 64-bit versions of Intel and AMD x86 chips incorporate more data storage slots called registers that can improve performance.

But Nack took pains to say that moving to 64 bits, while useful, isn't like flipping a switch that doubles performance.

Modest performance improvements
Based on Adobe's preliminary testing, the 64-bit version of Photoshop CS4 will give a performance kick of about 8 percent to 12 percent compared with the 32-bit version, Nack said. For one particular task--opening up a huge 3.2-gigapixel file on a system with a lot of memory--the 64-bit version is 10 times faster because it doesn't have to write the data that won't fit in memory onto a relatively slow hard drive.

In practice, a huge swath of Photoshop users won't be affected by the difference, at least initially. The transition from 32-bit to 64-bit computing has been creeping sluggishly across the personal-computing industry for years already, and it's going to be some more years before the transition is complete.

Advanced Micro Devices unveiled the first 64-bit x86 chip in 2003. Although AMD and Intel have moved their x86 processors to 64-bit designs, the new Mac OS X 10.5, Leopard, is Apple's first full-fledged 64-bit operating system, and Microsoft's 64-bit versions of Windows are almost unheard of in real-world use.

But it's not unreasonable to assume CS4 will have to hold down the fort until 2010 or so, when a PC with 8GB of memory will be ordinary, and by then, the difference between Photoshop on the Mac and Windows likely will be more glaring--especially for those users who already had a 64-bit Photoshop CS3 on their wish lists.

Fortunately for Mac users, Intel-based machines can run Windows either with a dual-boot configuration or through virtualization software, so perhaps that could tide them over if Adobe obliges with permissive licensing.

Open the 64-bit floodgates?
Today, most folks with PCs don't bump too hard against 4GB memory limits--indeed, it's not easy to find mainstream computing hardware with memory slots for more than 4GB even when there's a 64-bit chip and operating system. But Photoshop can be a taxing application.

Images are getting bigger and bigger, and Photoshop often is used to composite many together on multiple layers or stitch them together into large panoramas. At the same time, people are starting to store more detail in each pixel, moving from 24 bits of color information to 48 bits and, in the case of the high dynamic range photography (HDR), often even more. Having more memory also improves Photoshop's ability to track the history of changes to a file.

I suspect the Adobe shift will be a harbinger that the rest of the software industry is finally getting ready to make the 64-bit shift. The Photoshop user base is a coveted one, and making sure consumers have the hardware drivers and other technology they need will be a useful incentive for moving 64-bit coding up the priority list.

One group of programmers that will doubtless be quick to move to 64 bit are those who sell plug-ins for Photoshop. The 64-bit version will require 64-bit plug-ins, Nack said. "We can't mix 32-bit and 64-bit processes," he said, adding that Adobe has a prerelease development program that helps programmers make the move.

That Mac OS X will miss out on initial 64-bit Photoshop support is somewhat perverse. Apple has chosen a straightforward transition to 64 bits for its operating system and its new, widely adopted product has arrived. Apple's smoother change is possible in part because Mac OS X can still use older 32-bit driver software to support hardware, whereas Windows is available in separate 32-bit and 64-bit versions with corresponding drivers.

Microsoft began its 64-bit operating system transition with Windows XP, but it's putting more effort into the 64-bit version of Vista. Adobe expects 64-bit Photoshop to run on 64-bit XP, but only Vista will be supported, Nack said.

There are other Adobe Creative Suite applications, of course--the Premiere video-editing program springs to mind as another that could benefit from large-memory support--but Adobe isn't yet sharing details on those plans. It did announce Tuesday that Photoshop Lightroom version 2, which just entered beta testing, will be available in a 64-bit version. (Lightroom, for editing and cataloging raw photos from higher-end digital cameras, will work fine in 64-bit mode on Mac OS 10.5, Nack said.)

Other performance work
Nack and his boss, Kevin Connor, reiterated that 64-bit support doesn't mean a night-and-day performance improvement that Macs will miss out on.

"We fully expect that when we ship CS4, Mac users are going to be seeing performance improvements," Connor said.

And there are other hardware improvements besides 64-bit processors in the works. One big one is the increasing utility of graphics chips to process information as well as pump pixels to a screen.

"Graphics processors have become more powerful. We are very eager to take advantage of that power," Nack said.

What derailed the 64-bit train?
Until last June, Adobe had planned to move to 64 bit on Macs with CS4. But in June, Apple announced its technology plans at its Worldwide Developer Conference and that changed the situation for Adobe, Nack said.

Apple provides two technologies, Carbon and Cocoa, to help programmers take advantage of operating system services such as managing memory, fonts, or windows. Initially, Apple had planned to make both Carbon and Cocoa available in 64-bit incarnations, but Apple announced at the conference that only Cocoa would be.

Photoshop is written using Carbon, which dates from the earlier Mac OS 9 era and is better suited to cross-platform programming; Cocoa, like the newer Mac OS X, dates back to Jobs' previous company, Nextstep.

"When they chose not to do Carbon 64, we had to reevaluate our road map for getting there," Nack said. Adobe immediately assigned new programmers to the Cocoa switch "so we could make this transition as fast as possible, but as the saying goes, nine women can't make a baby in a month. You can only proceed at a certain pace," he said.

The amount of code that employs or interacts with Carbon features is substantial: about a million lines, and all of it must at least be reviewed, Nack said. Even today, "we don't yet know how much code needs to be rewritten or touched."

The Carbon-to-Cocoa switch was simply too massive to push back CS4 for just a couple months, he added.

"No one--Apple, Adobe, Microsoft--has attempted to move an application the size of Photoshop from Carbon to Cocoa," Nack said.

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