I'm building a new machine that will be used for both folding and crunching.  The plan is a 6850k cpu, evga x99 FTW K and 4x4gb of RAM.
However, regarding the RAM:
1. Would 2x8gb be just as fast?
2. Would 4x8gb be materially faster because it's dual rank?
3. How much of difference does speed make? Say 3000 vs 2400?
4. What about C15 vs C16?
 
Thanks in advance.
 
 

The speed or configuration doesn't matter as long as you have enough ram for the projects you are running for distributed computing afaik.

I would go with 32GB over Faster Memory for BOINC Crunching. 2400MHz Memory would be fine even 2133MHz as well.
Their are some Tasks, not many that need up to 2 GB per running Task.
So on an 4 Core 8 Thread 6 of these task would need 12 GB alone and you would be on the edge of running out of memory.
Then on some task like WCG they take very little memory to run, I have 58 tasks running and they take only 7% of 64 GB in all.
For Folding I see each running GPU Task taking up to 800 Megabits so allow 1 GB of Memory for Each GPU Folding.

Thank you.  I didn't realize there were 2GB tasks, and for $60 it was worth it to go with 32GB.

mektacular
Thank you.  I didn't realize there were 2GB tasks, and for $60 it was worth it to go with 32GB.

Well it is really 1.8GB for each task. Somewhere here on the Forums we have the info.
Sorry I have not yet found it, and I posted it. Getting Old

You should always populate all memory channels (in your case 4).  It can make a huge difference in performance on memory-intensive tasks.
WCG's Clean Energy Project runs best with 2GB per task, but the rest use much less.

Over at the BOINC signature page it shows the clean energy badge as being retired.
I haven't received a clean energy WU in a long time.
 

CEP is retired. CEP2 is not but has no work available at the moment. Therefore is technically "intermittent". The signature page may not have it accurate. RAM will perform better with all banks filled as Punchy mentioned. Each application in BOINC has its own needs. You will find that PrimeGrid really does benefit from faster RAM but other (many) will not. And there are projects with work units that go much higher than 2GB. The Lattice Project has seen it skyrocket up to like 16GB before. However, the virtualbox projects will sometimes require 3.5GB per. VDWnumbers will only continue to grow in the amount it requires. So, hit your personal goals now before it becomes too difficult.

Hay robbysites What is the Memory usage per task on SRBase?

You know this is good info that should go on out BOINC Crunching How To Thread.
What Happened to the Thread?