When I got my 2.8-GHz 8-core Mac Pro a few years ago, I did a bit of research on memory configurations, and the best information I found is that you want to fill all the available memory slots with matched memory pairs, since this maps to highest bandwidth, because (a) everything is matched and (b) all the slots are filled . . .
If I can find the article, I will post a link to it, but there were a lot of test configurations, and my take on it is that filling all the slots with matched pairs of equally valued memory is important, which makes intuitive sense . . .
So, I got the Other World Computing (OWC) upgrade to 8GB (6x1GB matched pairs), since the Mac Pro was the standard lowest-price configuration from Amazon.com and had 2GB (2x1GB) of memory, so the OWC upgrade was 6GB (6x1GB), which filled all the memory slots . . .
At present, I am running Mac OS X 10.6.8 in 64-bit kernel and extensions mode, and Activity Monitor shows that only 4GB of memory is used most of the time, which in part is due to nearly all the applications being 32-bit, although some of the newer IK Multimedia VST plug-ins are 64-bit . . .
And most of the time the 8 cores are utilized at perhaps 10 to 25 percent, which basically maps to the Mac Pro mostly not doing anywhere near what it is capable of doing, so my perspective at present is that 8GB of memory is plenty for Digital Performer 7.23 with a range of VST plug-ins like the Melodyne Editor (Celemony), TrackPlug 5, MultiDynamics 5, and Panorama 5 (Wave Arts), and ARC System, AmpliTube 3.6, CSR Classik Studio Reverb, and T-RackS 3.5 Deluxe (IK Multimedia) . . .
I use Notion 3 (Notion Music) and all the IK Multimedia virtual instruments and associated sound libraries, which I use to create "basic rhythm sections" that I then record in Digital Performer 7.23 via ReWire as soundbites, where for reference Notion 3 is a 32-bit application . . .
Once I get the "basic rhythm section" working nicely, I record real lead guitar and vocals in Digital Performer 7.23, but everything is based on the Notion 3 music notation foundation, which makes it easy to add additional orchestration later, so even when nothing initially comes to mind for orchestration I create a kick drum track and a piano track in Notion 3 that I use as the "click" track and "reference tuning" track in Digital Performer 7.23 so that all the real instruments and singing are synchronized with the music notation in Notion 3 . . .
This is the current song I am developing, and the instruments were mixed with loudspeaker monitoring after doing the ARC System calibration, but the single vocal track was done with headphones and a headphone mix. The vocal harmony is created by the Harmonator in AmpliTube 3.6, which is set to C Phyrgian, and I cloned the vocal track to create a second vocal track so that I could add more effects to it . . .
"(Baby You Were) Only Dreaming" (The Surf Whammys) -- MP3 (9.2MB, 276-kbps [VBR], approximately 4 minutes and 26 seconds)
Most of the time, I can compose and sing a melody in real-time on the fly on the first take, but there is a lot of instrumental counterpoint in the verses, so I did most of the verses as "melodic speaking", which is interesting as an experiment, but I plan to mute the instrumental counterpoint, which I think will make it easier to do an actual melody for the verses, which is fabulous . . .
Fabulous! 