DDR3 DRAM FAQs And Troubleshooting Guide

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clonazepam

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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?)

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.
 
Great article, Tradesman! I give it Two thumbs up and two big toes up too!

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?


 

nottheking

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I did spot an error already: the article gives the wrong definition of virtual memory. It's a common misconception that "virtual memory" simply encompasses the page file, but in the simplest terms, it's actually a step HIGHER on the hierarchy: It encompasses (or rather, points to) both physical memory and page file.

In a bit more precise/technical description, Virtual Memory is perhaps the oldest form of virtualization in widespread PC use: Intel introduced it to the PC market with their 80286 in 1982.

By "virtualization" it means that as far as each process and program is concerned, it has a FULL memory address range available to it, without having to be programmed to consider what other processes might be using at the exact same time. This is handled by the CPU's Memory Management Unit: it takes the entire range that a single process uses, and then maps that to ACTUAL addresses, distributing it so that there is no "overlap" where two processes wind up using the same space. (which very obviously could lead to problems)

Virutal memory predated the invention of the page file; originally, this meant that because there was a rather finite amount of physical memory, a single process would likely only get a fraction of the available space. A page file, however, allows the CPU's MMU to also map addresses to space on a HDD (or SSD today) so that it can have an effectively arbitrary amount of space, so that there can be even multiple processes that have more memory allocated to them than the machine has available physical memory.

In sum: Virtual Memory isn't a type of memory, it's a memory management technology. It's not tangible, it's "virtual," as the name implies. Page File is the actual space on a HDD/SSD used for extra RAM addresses.
 

Tradesman1

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In my article "DDR3 Performance: What Makes Memory Perform Better?" (link below) I ran some test using WinRAR with different DRAM data rates and configurations, then ran the same tests while running a number of other apps to quasi simulate a multi-tasking environment

http://www.tomshardware.co.uk/dram-benchmark-fluctuations,review-33154.html

this is an excerpt

"I'm not a big fan of most benchmarks, in large part because most of them don't really use the DRAM. In other words, there are lots of gaming benchmarks available, but most gaming is centered entirely on the CPU or the GPU, and DRAM isn't much more than a conduit for data to flow through. I've long said that having more higher-frequency DRAM tends to show the strength of it more when multitasking or using memory-intensive applications. Earlier, I used WinRAR as a benchmark to provide examples of changes between 2400 and 1600 DRAM, as well as in different amounts (8GB, 16GB and 32GB) at 2400. As I expected, the completion time took longer with the lower frequency of 1600 using 32GB, as well as when using smaller amounts of DRAM. Taking it a step further, though not something one can truly and fully quantify, I experimented with running multiple applications and then running WinRAR to compress the same file used earlier. The "simulation" consisted of opening 10 tabs in Chrome to a page that changes, running a Malware Bytes scan and running Geekbench along with WinRAR. I came up with these numbers (again, it's the average of the mid three of five tests) on the Intel system"


Original WinRAR Score Multitasking Score
2400 32GB 3.06 5.29
1600 32GB 4.01 6:56
2400 16GB 3.31 6:24
2400 8GB 4.16 8:13
When multitasking, you can see even bigger gains with the additional DRAM."

So while DRAM with higher data rates and more DRAM can improve performance even when simply single tasking, it tends to shine more when multi-tasking

T
 

Tradesman1

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DDR and DDR2 pretty much stuck to JEDEC standards and DDR4 is still in it's infancy of availability. , DDR3 which is the most common DRAM at present, is and has been for some time now has gone through numerous changes. Originally only intended to run up to 1600 (per JEDEC standards) , people wanted faster and faster DRAM and the manufacturers responded with 1866, 2000, 2133, 2400 and continue to expand to 3000 and higher. We had 2400 and 2666 before JEDEC ever got around to publishing (which were already outdated at the time) specs for 1866 and 2133. Additionally, the chip industry has changed, today most all DDR3 sticks are made using 4Gb memory ICs (chips) where earlier they were made with 2Gb, thus many older socket 775, 1156, etc mobos that were designed for the earlier versions of low density memory chips can't use the newer high density DRAM modules. We've also seen Kingston come out with DDR3 that runs off PnP rather than the more traditional and long standing XMP 'standard' .

Much of the above is covered more heavily in Part 2, which primarily explores myths and fiction related to DDR3, My working title for this piece was "DDR3: FAQs and Fiction" , it was intended as a 'troubleshooting guide', I'm not sure where that came from ;)

 

Tradesman1

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Part 2, as written primarily addresses additional common thoughts and statement, most of which aren't true or are often misconstrued, taken out of context.

Your last two points are ideas I have for articles, the first suggestion where Flex Mode is being used, would be a bit hard as there is never a guarantee when mixing DRAM - i.e. it's possible I could take a pair of 4GB sticks, say Brand A and Mix the with a 2GB stick, say Brand B, and it might work fine for me, but it's possible/probable the same mix of sticks won't work for most people who might try it. It's neveer a good idea to mix DRAM from different packages.


 

snir_va

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The description of physical vs virtual is not correct. Virtual memory is memory that has it's address translated through a memory management system. For example, every process can believe it's memory starts at zero and the hardware translates that to where the physical memory really resides. This is true with or without memory swapping to disk.
 

Tradesman1

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Thank you, that snippet was rather poorly written and should of been explained more in depth (as you have done). I've scheduled myself for 1,000 lashes ;)

As to the new rig, I primarily built it for use in helping people on the forums and testing/research, am fairly constantly changing components and also using for the Win10 beta

 

PaulBags

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Great article, Tradesman! I give it Two thumbs up and two big toes up too!

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?
The way it's explained in the article is each dimm is 64-bits wide, with dual etc channels meaning 2 or more dimms present as one device. If ganged presents as 128-bit wide then by this definition it would be two dimms in dual channel, where as unganged as two seperate 64-bit devices would be two dimms in single channel.

I would like to see the pros/coms of multi/single channel; it seems to me it would all still add up to the same bandwidth, but there must be a reason why they came up with dual etc.
 

Tradesman1

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Thank you, this is another area that I should have gone further in depth with. As I mentioned, early on in the piece, originally this was planned as a fairly straight forward informative article and just continually grew. In this particular section I should have titled it differently as I was thinking of the page file as the virtual disk, swap file as what most think of as the systems virtual memory. My apologies to all.
 

rdc85

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Thanks for info, I'm always confused about them, seems no different in performance if i chose one or another..
still not get about the pro or cons about choosing one or another...



One thing that I know to have benefit greatly of having big and fast RAM, is when running CHKDSK (checkdisk)..
It will fill your RAM in no time...

edit: great article btw..
 

Tradesman1

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"Thanks for info, I'm always confused about them, seems no different in performance if i chose one or another.. still not get about the pro or cons about choosing one or another..."

Yeah, unganged is a bit better with mutiple threads while ganged seems better with single threaded operations, most leave it as unganged

[

"edit: great article"

Thanx

 

nottheking

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Thank you, this is another area that I should have gone further in depth with. As I mentioned, early on in the piece, originally this was planned as a fairly straight forward informative article and just continually grew. In this particular section I should have titled it differently as I was thinking of the page file as the virtual disk, swap file as what most think of as the systems virtual memory. My apologies to all.
Not a problem to me. Mostly just that, since I predict this article will likely be an often-referenced one, (an opinion I can see I'm not alone in, judging by other other replies) it'd be best to make sure to avoid being misleading.

A corrected section likely wouldn't have to be anywhere NEAR as long as my reply there, (I'm more known for being thorough vs. concise) but should definitely specify that it's the "page file" is what the extra space on-disk is, and perhaps "virtual memory" can be abstracted to simply mean "technology that lets programs use all the memory space they want, including page file."
 

Dan414

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Great article, thanks!

Would love to see some common symptoms of a "bad" stick when you write the second half.

I had a second computer (for my boys) that I struggled with getting to run right for months - turned out to be bad memory. I had blue screens and random restarts until swapping in some known good memory.
 

Tradesman1

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Will check into this, I think it's doable, and again thank you for the input ;)



____________________
Symptoms can vary, and can actually include a number of possible causes, when you first put a rig together, it can be a good idea to run Memtest86 on each stick individually (running multiple sticks can actually cause false positive errors. I normally run 4-5 passes and if good leave things at that unless problems develop. Then down the road if you start getting unexplained BSODs, freezes, etc thet can be indicative of DRAM (or again, other) problems. Overall, DRAM failure rates are extremely low and of the 'failures', or DRAM that gets RMAed as defective, more often than not there's nothing wrong with the sticks, but the problems with the DRAM come from users not knowing how to set it up to run to spec or people trying to mix DRAM from different packages. The second part is already written and winding it's way through the system, the tentative publication date is 17 June, and has been titled "The Most Common DDR DRAM Myths Debunked.".

As written it covers the following 'myths' and is a continuation of this first piece,

It’s DDR3, all DDR3 is the same.
Just add more DRAM, it will be perfectly fine.
There are only a couple of companies that make DIMMS then they all get rebranded.
Your motherboard supports 3200 DRAM so you can use any DRAM you want.
Mixed DRAM can only run at the speed (or timings) of the slowest DIMM you are using.
Just buy 2 sets of two DIMMs rather than those more expensive 4 DIMM sets, it’s cheaper.
If you fill all four DRAM slots it will run faster.
You won’t see any performance gain with DRAM faster than 1600.
8GB is all anyone needs (or 8GB is all you’ll need for the next X Years).
You’ll never use or need 16GB (or 32GB or 64GB or….)
More DRAM won’t speed things up any.
A 64bit OS will let you run all the DRAM you want.
1.65 DRAM will damage your Intel CPU.
Putting DRAM in dual channel doubles the data rate, or is twice as fast.





 
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