CFD Online Logo CFD Online URL
www.cfd-online.com
[Sponsors]
Home > Forums > General Forums > Hardware

Help with RAM choice for Fluent Simulations!!!

Register Blogs Members List Search Today's Posts Mark Forums Read

Reply
 
LinkBack Thread Tools Search this Thread Display Modes
Old   December 23, 2011, 20:07
Default Help with RAM choice for Fluent Simulations!!!
  #1
spk
Member
 
Join Date: Aug 2009
Posts: 67
Rep Power: 16
spk is on a distinguished road
Hi guys,

I' m between four RAM choices in order to run demanding Fluent Simulations!

6GB 7-8-7-20 1600MHz
6GB 9-9-9-24 2000MHz
12GB 9-9-9-24 1600MHZ
12GB 9-10-9-27 2000MHz

What is the best solution to achieve:
1) run a simulation faster
2) run a grid with 2-3 million cells or more
3) run many fluent simulations parallel

or which characteristic of RAM (size, speed rating and tested latency)
affects 1) 2) and 3)??

Thanks,
spk
spk is offline   Reply With Quote

Old   December 24, 2011, 06:51
Default
  #2
spk
Member
 
Join Date: Aug 2009
Posts: 67
Rep Power: 16
spk is on a distinguished road
I think i' ll choose 12 GB to run more cells!
My question now is between these RAM, which is faster?
12GB 9-9-9-24 1600MHZ
12GB 9-10-9-27 2000MHz

I read a previous thread in this forum that a change from 1600MHz to 2000MHz speeds up only 10%. How the tested latency affects the RAM speed?
spk is offline   Reply With Quote

Old   January 6, 2012, 16:00
Default
  #3
New Member
 
Sebek
Join Date: Jan 2012
Posts: 7
Rep Power: 14
GTCo8 is on a distinguished road
Buy better 24 GB of cheaper RAM (with worse timing) than 12 GB. RAM is now very cheap. I can recommend OCZ, G.Skill, Patriot or GEIL modules
GTCo8 is offline   Reply With Quote

Old   January 28, 2012, 17:11
Default
  #4
Member
 
Join Date: Jul 2011
Posts: 59
Rep Power: 14
rmh26 is on a distinguished road
You might need to make sure your cpu/motherboard can handle ram at 2000. The westmere xeon's I got last year only officially support ram at 1333. Could probably mess around a little with them to get them to run higher speeds.

Faster ram will help, not sure if you need the extra capacity if you only doing 2-3 mil
rmh26 is offline   Reply With Quote

Old   January 28, 2012, 17:52
Default
  #5
spk
Member
 
Join Date: Aug 2009
Posts: 67
Rep Power: 16
spk is on a distinguished road
Thanks for the answers!!

Do you know how many cells can solve with 24GB or 32GB ram?
spk is offline   Reply With Quote

Old   January 28, 2012, 19:35
Default
  #6
spk
Member
 
Join Date: Aug 2009
Posts: 67
Rep Power: 16
spk is on a distinguished road
I have also an another question!
I think to buy a motherboard with 8 slots with 64GB max.
One 6-core CPU could use all this memory 64GB?
spk is offline   Reply With Quote

Old   January 30, 2012, 11:54
Default
  #7
Member
 
Join Date: Jul 2011
Posts: 59
Rep Power: 14
rmh26 is on a distinguished road
Just for fun ran some tests on the 2-d code I'm working on. I have a 24gb of ram in 6 4gb chips. I managed to max out at roughly 64 million cells. This code have several extra fields it has to worry about because it is a two phase model on a staggered grid, and I probably could optimize it for memory and get the cell count into the 100's of millions.

That being said I rarely go over a million or two cells because the simulations just take so long. I would say you would run out of cpu power long before you run out of addressable memory. So while you could buy 64gb of RAM you probably couldn't solve any problem that used all 64gb. Better choice would be to buy lower capacity, faster ram. For regular grids you will tend to be bound by memory access.

You are correct though in the ram speed question, roughly a ten percent increase in speed between the two timings you lists. The faster ram has slower timings so the increase isn't as much.

Yes your processor could access all the ram as long as the mother board supports it. Just because a processor has tri-channel or quad-channel memory doesn't mean it can only access three or hour memory chips.


If you really want to do large simulations >10 mill cells it might help to get a gpu, although I'm not sure if fluent supports them and if they do it probably costs extra.
rmh26 is offline   Reply With Quote

Old   January 31, 2012, 12:44
Default
  #8
spk
Member
 
Join Date: Aug 2009
Posts: 67
Rep Power: 16
spk is on a distinguished road
Quote:
Originally Posted by rmh26 View Post
Just for fun ran some tests on the 2-d code I'm working on. I have a 24gb of ram in 6 4gb chips. I managed to max out at roughly 64 million cells. This code have several extra fields it has to worry about because it is a two phase model on a staggered grid, and I probably could optimize it for memory and get the cell count into the 100's of millions.

That being said I rarely go over a million or two cells because the simulations just take so long. I would say you would run out of cpu power long before you run out of addressable memory. So while you could buy 64gb of RAM you probably couldn't solve any problem that used all 64gb. Better choice would be to buy lower capacity, faster ram. For regular grids you will tend to be bound by memory access.

You are correct though in the ram speed question, roughly a ten percent increase in speed between the two timings you lists. The faster ram has slower timings so the increase isn't as much.

Yes your processor could access all the ram as long as the mother board supports it. Just because a processor has tri-channel or quad-channel memory doesn't mean it can only access three or hour memory chips.


If you really want to do large simulations >10 mill cells it might help to get a gpu, although I'm not sure if fluent supports them and if they do it probably costs extra.
Thanks a lot!!
Do you think that i would run out of 4-core cpu power long before i run out of a 32 GB memory?
Or do you suggest me 24 GB?
spk is offline   Reply With Quote

Old   January 31, 2012, 14:16
Default
  #9
Member
 
Join Date: Jul 2011
Posts: 59
Rep Power: 14
rmh26 is on a distinguished road
It really depends on what type of problem you are solving but if your expecting to get results back in a reasonable time then your probably not looking at solving problems with more than a couple mil variables.

For reference the jaguar super computer consists of compute nodes with dual hex core AMD processors with a total ram of 16GB. This is 1.3 Gb RAM per core.
rmh26 is offline   Reply With Quote

Reply

Thread Tools Search this Thread
Search this Thread:

Advanced Search
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are On
Refbacks are On


Similar Threads
Thread Thread Starter Forum Replies Last Post
Fluent uses too much RAM Komon FLUENT 0 December 11, 2011 12:10
Hardware selection for steady/unsteady incompressible, turbulent and cht simulations maddalena OpenFOAM 2 July 13, 2011 09:55
Increasing RAM decreases CPU time!!! Melih GULEREN FLUENT 2 April 5, 2004 07:21
URANS and Transient Simulations bob Main CFD Forum 0 October 1, 2003 04:54
Can FLUENT run under Linux with 2 Gb of RAM? Paul Gregory FLUENT 0 February 13, 2001 21:10


All times are GMT -4. The time now is 00:44.