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.
Yes you can thank your Steve Jobs for that. Man I would have loved to see the looks of those avid Apple fanboys and fangirls when they read this....
Incidentally if you are an Apple fan please take a picture of your face at the end of this message so that I may gloat some more.
Finally i actually feel lucky to be running windows vista 64bit.
"I must not fear. Fear is the mind-killer. Fear is the little-death that brings total obliteration. I will face my fear. I will permit it to pass over me and through me. And when it has gone past I will turn the inner eye to see its path. Where the fear has gone there will be nothing. Only I will remain."
--- Frank Herbert, Dune - Bene Gesserit Litany Against Fear
Check out my Sketchbook! Critique and Criticism welcomed.
There are a lot of people (around here, boo!) still running Photoshop 7, so the decision of skipping one version isn't a big one. Adobe will eventually switch to 64-Bit for Mac OS X. It might just not be in CS4, but in CS5.
So, no big deal.
(EDIT: I'm running both Vista and OS X for apparent reasons)