Memtest for Windows is much more sensitive to Ram problems compared to the Memtest86+ boot CD. I've read through many forums where others have come to this same conclusion.
 
 It's the only one I use anymore because the boot CD takes much longer to find errors on bad Ram or it never finds the errors at all. 

It's best to run the test at least 300% if you are testing an overclock or just to make sure your new Ram is good.
 
 If you are having stablity or freezing problems that you think might be related to your Ram then testing over night at least 8-10 hours will find any and all Ram problems.

For a Quad core processor open up 4 instances of Memtest then divide the unused Ram by 4 and type that amount into all 4 instances of Memtest then start them all up. This will load all your cores to nearly 100 percent and eventually test all of your Ram.  
 
For a dual core processor you only need to run 2 instances of Memtest. To figure out how much Ram to test you need too divide the unused Ram in half and type that number into Memtest then start both of them up.

For 4GB of Ram and a dual core processor that is using 25% of system Ram 4GB= 4000MB - 25%=3000MB/2= 1500MB, so you would type 1500 into each instance and run them both at the same time.
 
 This will stress both cores to 100% and eventually will test all the Ram if you run the test long enough. Testing to 300% is standard but testing overnight will sort out any and all Ram problems that you might be having.
 
 For testing "8GB" and a Quad core processor..if you are using 25% of your system Ram type in 1500mb into each and start up all 4 instances of Memtest.
8GB=8000MB - 25%=6000MB/4=1500MB Per instance.


For testing "4GB" and a Quad core processor..if you are using 25% of your system Ram type in 750mb per instance of Memtest.
4GB=4000mb - 25%=3000/4=750mb.
 
Example for a Quad core process using 4GB Ram with 30% used Ram.
4GB=4000mb - 30%=2800/4=700mb per instance of Memtest.  

For I7 and 8 cores run 8 instances of Memtest and divide your unused Ram by 8 then type that number into each instance of Memtest.
 
This is how you want it to look using a Quad core processor and 4GB Ram. Example below using 4GB Ram with 25% of system Ram being used. 


 

Download this free program here: http://hcidesign.com/memtest/download.html

I use this one to determine how much physical used Ram.
 


Or you can use Everest also.
 


 You can also use the resource meter which may be more accurate.
 




Testing in pairs using the black slots is probably the fastest way to find bad Ram. It can take much longer if all 4 Dimm slots are full. Testing over night will sniff out bad Ram completely and eliminate any chance of bad Ram. Testing one stick in the black slot closest to the CPU will show errors even faster if it's bad.

I dont think I've ever found any errors using the Memtest86+ boot CD but I'm sure it works for certain types of problems. The CD is not nearly as sensitive to errors as the Windows version so I highly recommend using the Windows version of Memtest.

Mac_vista64

With 6GB I ran about 15 instances of memtest @ 256MB each and let each run 5-6 cycles.
Why run only two?

 
Who said anything about running two instances, that would only be for a dual core processor.
 
 I showed 4 instances for a quad core and said that you need to run one instance for each core for i7.
 
 I think you need to read a bit closer because you only need to run 8 instances then just divide your unused Ram into those 8 instances.
 
Here is what I said, second line from the bottom....
For I7 and 8 cores run 8 instances of Memtest and divide your unused Ram by 8 then type that number into each instance of Memtest.
 
Seems fairly obvious to me.

You can run the test however you want but I didn't make up these directions, running one instance per-core is exactly what the memtest site tells you to do.  The problem was that the directions were rather vague and poorly written with no pictures and needed some clairifcation. 

There is also no valid reason what so ever for running more instances than the number of cores you have. Is a matter of fact if you do it that way you would be doing it incorrectly according to the Memtest website.

I also have another paid version of the Memtest that Automatically adjusts the number of tests to the number of processor core's being run but that one costs money and most here won't be using it. Needless to say it runs one test per core automatically and also adjusts the amount of Memory being tested. Kinda worth it if you ask me.   
  
This post already has more hits than any of the other sticky's, so why was it removed from the sticky's in the first place? 

klepp0906

chevell
There is also no valid reason what so ever for running more instances than the number of cores you have.

Then why are you instructing people to run 8 instances when octacore cpu's aren't even out yet? Is it core's or threads?  4 cores + 4 threads w/ Hyperthreading then 8 instances sure, although im not convinced that's even necessary considering this is supposed to be for memory.  What purpose does loading up the cpu have?  Or is it just in an attempt to make it take less time?

Chevell hasn't been on the forums for the past 15 months. Don't be surprised if he doesn't answer you back anytime soon.        

Link is still broken, so no, it isn't just you.