We've established here that setting Mechanica's memory allocation to around half your available memory is still a pretty good guideline, even though that's more likely to mean 6 GB than the 128 MB default.
In my team we're getting some amazing performance using a RAM drive to supplement WF4's 8 GB Mechanica limit, and it's a very useful (and usable) tool these days.
However, this number doesn't seem to be a hard limit - to copy from a recent .rpt file:
Memory and Disk Usage:
Machine Type: Windows XP 64 Bit Edition
RAM Allocation for Solver (megabytes): 8192.0
Total Elapsed Time (seconds): 5162.19
Total CPU Time (seconds): 3089.44
Maximum Memory Usage (kilobytes): 19861061
Working Directory Disk Usage (kilobytes): 18542428
Results Directory Size (kilobytes):
5172630 i:\casing_dyn_3rd_3mounts_3casings
Very small components usually do only use around 8 GB, but as the run gets bigger so does the memory take by msengine.exe, and I suspect that this recent run started hitting the Windows swapfile (20 GB Mechanica + 6 GB RAM drive + xtop + Windows on a 24 GB machine...) - which can't be a good thing!
What's the exact relationship between the memory allocation setting and what msengine.exe actually uses? By trial and error we'll probably turn it down to 6144 next time, but as each model is different it's a little hard to predict for a new run.
Thanks!