Yesterday I went to my local Apple store and gave the stock 4 core 2.66 Mac Pro a little stress test. I prepared a Logic project with alternating ES2's and Sculpture on each channel strip with a different stock patch selected on each channel, with a simple MIDI region 1/4 notes for 4 measure. I also had a delay designer, ad-limiter, and space designer inserted with stock patches on each channel strip. I tried to pick the most stressful patches (i.e. long space designer delays, complex delay designer patches).
The 4 core machine showed 8 CPU's in Logic's performance meter and the CPU load seemed to scale across them pretty well. I got 27 tracks of this going and roughly 60% cpu usage on each core. I then added a channel EQ per track, opened the channel EQ plug ins on the screen and turned on the channel EQ analyser for each channel to further stress the meters.
I forget the exact sequence of events at this point but I got tired of adding channels and started to copy the MIDI regions on each track and overlap them to increase the polyphony load of each soft synth and that's when the machine started to get a bit bogged down. The channel meters started to slow down and get choppy, I then closed each channel strip to get rid of the analyser refresh loads and the Channel strips became much more responsive. Eventually I got a CPU overload, but it took a while. I think copying the MIDI regions over each other finally brought the system to an overload.
To get rid of the overloads I needed to option click on the soft synths and plug-ins, simply muting the tracks didn't seem to have much effect. It's hard to say what exactly started to bog the system down the stock system had only 3 gigs so memory issues may have been at play along with CPU loads.
I'd love to try this on a stock 8 core Nehalem to see how well Logic scales across all 16 virtual cores to see if the 8 core machine is worth the price difference, but there aren't any on display at any Apple stores in the SF bay area. I'd like to compare the effects of the faster clock on the 4 core machines against the slower clock speed 8 cores to see what makes more of a real world difference.
But the bottom line is any of these machines is really quite powerful for complex music production. My 2.4 MacBook Pro seems like a toy compared to the 4 core Nehalem Mac Pro. I might go for a 2.9 quad with 8 gigs of memory and wait a year for the 4 gig SIMMS to come down in price before upgrading to 16 gigs. But I'm hoping to check out the stock 8 core machine if I can find one before making a final call.
Does anyone have any stress results for the new 8 core machines?