Photoshop CS5 very slow performance, MacBook Pro i7

Question

Hi, I've noticed some posts on slow screen redraw, but my issue seems to be with specific performance with web based files having many layers and layer groups.
A sample file is a 27mb psd. It has lot of layers (525), mostly type layers (limited to 3-4 typefaces in the file) and layer groups. If I select a particularly large layer group and try to move it on the canvas, I get the Adobe throbber cursor icon for at least 20 seconds. Even small layer groups bring up the throbber cursor for a few seconds. Overall, things seem much slower than CS4. Not good! And I'm just speaking of basic operations, not hitting intensive tools or major filters yet.
I've looked at the site below, but not much information except the option to purchase some scripts to 'warm-up' Photoshop. After what I spent on Design Premium, I don't think I should have to purchase third party scripts to warm it up. (I did experiment with the tiles option under performance pref's, but upping that made opening files take 2 minutes, where before opening was achieved in 10-15 seconds.
http://macperformanceguide.com/index_topics.html#OptimizingPhotoshopCS5
I have a brand new MacBook Pro i7, 8GB, 7200 internal drive. I installed everything from a fresh install of Snow Leopard. CS4 has never been installed on this Mac.
Any thoughts?

Answer 1

if you have 4GB RAM, the system would need about 1-2GB,
so if you quit all other apps and only run PS, it has 2-3GB RAM left.
you can set RAM-usage in percentage, in the settings menu of photoshop,
i set it to 70%, the rest is for osx.
so lets say PS uses 2GB RAM in your case, the more hires images you open at once and the more layers they have,
and the bigger they are, the 2GB RAM are gone and PS will use the scratch disc for the mentioned images you opened at once, which is also configured in the settings menu. usage of a scratch disc (PS writes data to the scratch disc permanently) will slow down overall performance, it may lagg and everything is slower than before (in my experience). best for scratch disc usage is a separate, fast, internal disc, as huge as possible (50-250GB discsize and empty, no files on it, so that PS can write continously, in order to avoid disc-fragmentation, which would slow down the writing process additionally)
thats the reason i would add 8GB RAM.
RAM is very important for photoshop CS5.
(also processor clock speed and number of cores - in the moment 2 cores are enough
as CS5 isnt optimized yet for more than 4 or 6 cores. more to come soon, i hope...
in my case, i added 24GB RAM, cause i want to avoid usage of a scratch disc at all. this is a huge gain of performance for myself.
i never liked my old scratch disc, as working was terrible slow with it. i also had only 4GB RAM in my last mac, and working was no fun
i work on large format files, 50-100cm at 300dpi and lots of layers, each layer has to be seen like an image itself, so each layer rises RAM consumption.
its a pitty that i never saw adobe delivering some kind of performance guide for photoshop, how to improve performance for professional users, like posting that guide on their main photoshop site, i had to digg for these informations for a long period of time and found it in the end at diglloyd´s comprehensive site. i wonder why adobe makes a secret about photoshop performance, a lot of my friends at work mentioned formerly, that they have had huge lag issues and dont know where to begin solving these problems, which are solvable for sure.... (new hardware, proper settings and so on)
you can read detailed instructions, on how to speed up things in PS here: (where i took it for myself)
http://macperformanceguide.com/index_topics.html
subtopic:
http://macperformanceguide.com/OptimizingPhotoshopCS5-Intro.html
enjoy your new macbookpro!
peter