As with every designer we colaborate with, mentions the Photoshop CS5 problem. The key difference between Photoshop CS4 and CS5 is that  CS5 is a full 64-bit application. This is what Adobe says caused it so much work and delay; rewriting the user interface from Carbon to Cocoa.

Photoshop CS5 does have new features, but for those working with huge files, the 64-bit part is essential. It means that working with bigger files can be much faster, because operations can be performed in RAM.

The days of the scratch volume are over for Mac Pro users with adequate memory (excepting really monster jobs exceeding 60GB or so).

Memory usage

Memory in 32-bit CS5 is limited to 2100MB, nearly 1GB less than with Photoshop CS4 (3072MB vs 2100MB).

Problem is, many 32-bit plugins require 32-bit mode until new versions arrive. The only workaround seems to be run both CS4 and CS5 simultaneously.

The Cache Tile Size setting is a load of crap also. I mean… makes no sense!? The recommended default setting yields hugely impaired performance. And using a preset is well running blind. Adobe states “To quickly optimize these settings, click a preset…”. Rubbish!!! This is a careless decision (or maybe mistake). Something else should be done, perhaps maybe CS5 figuring it out automatically (self analysis).

Let’s just say that the performance levels were not to my liking. In fact, Photoshop CS5 performed worse than CS4. I was even more confused because Adobe touted the 64-bit nature of Phototshop CS5, which was supposed to bring all sorts of performance gains. I saw none of these, and in fact the opposite.

The Rotate View tool was sluggish and jumpy, brush resizing via the keyboard was jerky at times, zooming in and out was full of hiccups and lag.

Lest you think I’ve been holding on to some old outdated machine, I’m running a Mac Pro dual-quad 3.2 Ghz with 24 GB of RAM. And like I said, CS4 was blazingly fast for me. I was really disappointed in the upgrade. In fact, I was reverting back to using CS4 for my Photoshop needs.

Reaching the end of my rope, I finally did a Google search. I found the Mac Performance Guide article all about Optimizing Photoshop CS5 Performance.

The series of articles explains that most of the tips for CS4 were valid, but there were a few things specific to CS5 that could use a little work. In particular, the one tip that helped me was the Cache Tile Size tip. Seems this obscure little setting in the preferences has a huge impact on Photoshop CS5’s performance, and oddly it’s set by default to a number that kills Photoshop’s performance by up to 80% in some cases!

There’s also a Memory Allocation issue which — as the author suggests — is a bug and needs to be fixed by Adobe.

For general use, I’d probably use a history of 50 or so, because I like history then to these settings…

1024kb Cache   –   15 History   –   3 Cache levels
don’t even think about using 128K tiles with big files.