DDR DRAM FAQs And Troubleshooting Guide
References
By Jim Reece
published DRAM is probably one of least understood components in a computer. Here are answers to our readers’ most common questions about memory.
Physical Versus Virtual Memory?
Physical memory is what actually exists on your DIMMs, whereas virtual memory is an area of your hard disk that is set aside for the system page file (also referred to as the swap file, or virtual disk). As your physical memory fills, the system will cache data that is likely to be accessed again soon to the page file. That way, it can reacquire it faster than it would if it had to reach out to a website or reopen a file, for example.
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47 Comments
Comment from the forums
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das_stig With AMD motherboards, you should set the memory to unganged mode for a tiny performance improvement unless you're running a webserver.Reply -
Mahruay Nice read although could you explain what real world improvements can be seen in faster RAM.Reply -
boju Nice article, answers a lot for people and definitely will link for future references. I need to ask though, is there any reason to discriminate DDR3 as per title?Reply -
clonazepam I hope the next part covers performance when using say 3 sticks, where 2 are dual channel, 1 is single channel. Some real world results would be stellar (maybe as a follow-up?)Reply
I'd also like to see RAM drives covered. Suppose you allocate 4GB out of 16 for a RAM drive. How does the software create the 4GB? Is it using a single chunk of memory, is it taking 1GB from each of the 4 sticks? Is it from the beginning, middle or end of the 16GB of memory?
Covering how to identify true "memory leaks" versus a more common scenario where RAM usage grows intentionally from the caching of more and more assets. -
damric Great article, Tradesman! I give it Two thumbs up and two big toes up too!Reply
Only 1 issue:
Ganged vs Unganged: that actually doesn't have to do with single or dual channel.
Quote AMD:
Ganged mode means that there is a single 128bit wide dual-channel DRAM Controller (DCT)
enabled. Unganged mode enables two 64bit wide DRAM Controllers (DCT0 and DCT1).
The recommended setting in most cases is the Unganged memory mode. Ganged mode may allow slightly
higher Memory performance tuning and performs well in single-threaded benchmarks.
Depending on the motherboard and BIOS, it may be required manually setting the timing parameters for each
DCT (in Unganged mode) when performance tuning the memory or fine tuning the timings. Some BIOS
versions apply the same timings automatically for both DCTs in an Unganged mode.
Unganged is like a normal divided highway with two directions. Ganged let's traffic use all of the lanes in one direction at a time. Unganged is said to be more efficient but no one really ever tested this thoroughly to see if any applications would be better served in ganged instead. You could still have unganged single channel or dual channel, and ganged single channel or dual channel. If that's confusing I'll try to explain with more complicated interstate highway anecdote.
Lastly, I see you have a new AMD rig. Did your head explode when you saw how much more difficult it is to tune memory on that platform than on your past intel rigs?
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Shankovich Awesome article! These kinds of articles is what brought me to Tom's in the first place years ago!Reply