CPU selection
CPU selection
(OP)
I'm in the process of configuring a new system to run Ansys, and I'm wondering if the Pentium D Dual Core cpu is better or worse than the Xeon chips? Does Ansys take advantage of the dual core processor?
thanks, TJ
thanks, TJ





RE: CPU selection
Just a warning though - my experience has been that the limiting factor in solution speed is NOT processor speed (or number of processors), but rather memory. I would highly recommend that you investigate a 64-bit option and then purchase as much memory as you can afford. You're money is probably better spent on memory than extra processors.
My 2-cents.
RE: CPU selection
TJ
RE: CPU selection
From my perspective, Linux is the way to go. However, this would likely throw a monkey-wrench in your old 32-bit windows apps. Definitely no easy solution.
RE: CPU selection
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RE: CPU selection
thanks again,
TJ
RE: CPU selection
BTW, Drej was right that some parts of ANSYS do not parallelize (for two processors - like I have) or multiplize (for more than two processors - like I wish I had) - namely the graphical boolean operations and some of the meshing. However, I can verify that the PCG solver and the Sparse solers both seem to optimize the amount of work performed on more than one processor. Since the majority of your "wait time" will be during solve, I woudl classify this as essentially well optimized for multiple processors.
RE: CPU selection
from what I understood, most of ANSYS solvers don't "really" parallelize, i.e. they don't divide the job into "sub-systems" to be solved parallelly. It's rather Windows that tries to "balance" the load between the processors by switching the threads. Effectively, if you keep a Task Manager open when Ansys solves, you will see that it calls much more than a single thread, so the presence of several processors can be beneficial anyway.
It is a matter of fact that Linux / SCO Unix are the best platforms for computationally-intensive tasks. If I were you, I'd set up a dual-O.S., using Linux for most of the job (note that OpenOffice, among others, has a very good compatibility with MS Office; Mathematica exists in Unix version, and so does Matlab I think.
About memory, I can add some info: at my company, we recently ran a 900000 elems, >2000000 dofs, using PCG solver, on a Dual-Xeon with 3GB RAM: the CPU indicators reached 100% occupancy only for a few seconds, averagely it was 90% + 50/60%, but the available memory dropped under 4000 kB several times!
Another 2-cents: I would consider a VERY fast raid-array of SCSI discs: despite the memory availability, ANSYS writes/reads a lot... For several operations, very huge files are written, parked, and then re-read...
Level2-cache speeds-up the whole processing subsystem, so it has been benchmarked several times that going from 512kB to 1MB and then to 2MB produces noticeable effects.
Regards
RE: CPU selection
W.r.t. the array of fast SCSI disks - six months ago I would have agreed with you. Now, with 16GB of RAM, I find that the only rading/writing from/to disk is with a SAVE/RESUME. It's unbelievable the speed-up that I have seen. I performed on analysis that took almost an hour when I solved it on my 32-bit XP boot. Then, when I booted into 64-bit Linux, it took 17 minutes!! Al because of the added memory-addressign capability of the 64-bit OS. Can't go wrong with that.
Cheers