I'm running on a Dual Core AMD 4600+ at 2.4ghz, 2GB ram, scratch disc set to another physical hard drive (very important!) and maximum amont of ram PS can use is bumped up to 90% (I've heard this is not recommended but so far no issues for me). Cache, can't remember, think I left it at the default...
If you guys are looking for a performance boost, 2 of the best things to do are:
1. Up your ram to at least 1gb, 2gb is better of course but not so much if you seldom do poster sized stuff.
2. Scratch disc set it to ANOTHER PHYSICAL DRIVE, not even a partition, physically another drive...
The 2nd suggestion is, from experience, can give you the most performance boost...
Also, for this particular piece, very seldom were filters used, most of the time it's just the simple brush tools which are a lot less taxing on the computer. If for example I use the liquify filter on this then I'll be in trouble...
Yeaps!
Erv.