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Dual vs Quad Channel, any impact on which ram I can use?

Sinept
Level 7
So I'm building a pc, and I haven't bought my ram yet. I was initially going to buy 2x8GB ramcards, but as 1x16GB is the same price, and makes upgrading later less of a hassle (and cost), I've been considering buying a 1x16GB card instead. But while searching for information about any performance differences (purely out of curiosity), I came across a few posts—I don't know where now, as it's been a few days—which stated something along the lines of 16GB requiring quad channel ram support; and after reading about quad vs dual channels, I'd also become concerned about whether 4x16GB ram, or 4xanyGB ram is off the table (all this despite having 4 slots and a board which lists 64GB max ram in it's specs). I emailed tech support while waiting for my account here to be verified, and received this response:

"If you wants quad channel setup, please use X99 motherboard with processor that supports it.
Dual Channel: Dual-channel-enabled memory controllers in a PC system architecture utilize two 64-bit data channels: 3200*2=6400 total bandwidth
Quadl chnanel - supports arcitecture that utilize 4 channels: 3200*4=12800"

What I'm taking from this, is that dual channel supports 64GB of ram, and quad channel supports double that. Is that correct?
Should my board have any trouble running 16GB ram cards? It's a Hero IX, btw (dual channel).
I eventually want to run 2x16GB, and may even upgrade to 4x16GB, if I find that I can utilize that much.
I should mention that I'm pretty sure I have nothing to worry about, but I'd still like to be reassured.

BTW, if you're interested, my full component list currently includes a corsair carbide case, Hero IX MB, i7 7700k cpu, cooler master 612 V2 cpu cooler (I wanted an air cooler because I read that liquid coolers could dry out, leak or explode, and destroy my pc), and a corsair cx750m psu.
(image for reference)
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Components which I intend to buy and install include 2x16GB corsair vengeance c15 3000Mhz ramcards, 1 samsung 960 pro 512GB storage card (for OS and in-use programs), 1 WD 1TB HDD (for extra storage and backup), a blue ray drive/burner (I'm not sure which yet, as I've read that there's a new blue ray standard on the horizon, for which drives are just now being manufactured, but aren't quite available yet; and I don't know if my board is equipped to handle one), a Strix 1080 ti GPU, and windows 10. I'm also convinced that I'll need a 144Hz 4k monitor with G-sync, and maybe some decent speakers/headphones (I won't need a headset as I don't play online games).
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10 REPLIES 10

Arne_Saknussemm
Level 40
Have a read of this https://rog.asus.com/forum/showthread.php?57038-Don%92t-combine-memory-kits!-The-meat-and-potatoes-o...

Buy a single kit of whatever size and frequency you want...don't think of adding RAM in the future.

If you want to populate all 4 slots buy a single kit rated quad/dual channel.

or buy a single dual channel kit of 2 sticks.

Sinept
Level 7
Thanks for the advice, but 4 card kits aren't available at the moment (edit: actually they are, if you're willing to pay extra for pretty lights) , and as I would be buying 4 of the same model card, which are also the same exact cards that are sold together in 4 piece kits (advertised on corsair's website, but not actually available for purchase from any retailers, including corsair), I'm not convinced that there would be any problems. I may go ahead and buy a 32GB set though, just to be safe. (I may not ever actually need 64GB anyway)

update: after a bit more reading (and some fact checking), it seems that the difference is in the testing and binning process used to match cards for best performance and stability. Even so, I'm not willing to pay for a full 64GB kit right now, so I'll settle for a 32GB kit and if I decide to upgrade I'll buy a full 64GB kit and resell or reuse the 32GB kit. I won't be using any virtual machines or a ramdisk, so I probably won't need more than 32GB. (I read that windows 10 will aggressively cache ram, and if so I may need to change some settings, but my windows 8 rarely uses even half of it's 8GB stock ram, even when running multiple programs, so I may have read some hyperbole. This guy has 128GB ram according to his screenshot, and the 7GB in use and 6GB cached uses maybe 10% of his total ram capacity. either windows is happy to waste ram when you have an insane amount, or google chrome really does suck).

Chino
Level 15
What capacity and speed are you aiming for? Also what's your budget and where do you plan to buy the memory kit?

Sinept
Level 7
I'm probably going to go with 32GB (2x16GB) of c15 3000Mhz ram from Corsair's Vengeance series. I may order it from corsair's website; or otherwise from Amazon. The current price is $270. I was initially going to purchase 16GB of ram and add more later, but Arne advised me against it. I still need to buy my storage, BR drive, OS, Monitor and accessories, and also a graphics card (probably a strix 1080 ti). My budget is whatever I'm willing to pay for individual components, as I haven't set aside any specific amount for this build (I expect it to be complete by maybe Christmas). The overall ammount that I expect to spend is around ~$2500 (and possibly up to $3000 with accessories), and I'm ~$900 in with my case, MB, CPU, Cooler and PSU.

Zka17
Level 16
Check your motherboard's QVL for a memory kit - that is your best shot... you can look for 2x8GB or 2x16GB kits - do not mix different kits!

Chino
Level 15
The CMU32GX4M4C3000C15R is a very nice 4 DIMM DDR4-3000 kit that's going for $254.99 at Newegg. But if you're looking for a 2 DIMM kit, the CMD32GX4M2B3000C15 and CMK32GX4M2B3000C15 are both good options that you can find for around $249.99.

Korth
Level 14
Agreed with Arne and Chino and Zka, lol, repeating their advice for emphasis. Do not buy your DDR4 with the plan of filling some slots now and populating the empty slots later. Mixed and mismatched DDR4 sticks will be incompatible, cause system instabilities, limit performance and reliability, compromise your data, and waste many hours with frustrating tweaking and rebooting - not at all worth "saving" a little money in the long run. Especially since in the long run you'll end up having to buy the bigger/better kit anyways and trying to resell your existing one at a loss.

My employer recently installed a pair of DDR3/DDR4 analyzers in our workshop - a Teledyne-LeCroy Kibra 480 and a Nexus MA4100, along with a variety of probes, interposers, add-ons, and accessories - for (I'm told) about $50K or $60K CDN. These instruments provide all sorts of complex metrics about DDR4 sticks (or chips), right down to realtime dB signal losses (at picosecond and millivolt resolutions) on individual pins and traces. I've operated the machines (on my own DDR4 motherboards, lol) but I won't pretend to be expert on everything they tell me about memory. Suffice to say that beyond the primary and secondary and tertiary timings there are also guardbands and impedances and quite a few other quirky parameters in each of your DDR4 memory sticks which all have to mesh perfectly (with your motherboard, processor, and each other) for your system to work - all the sticks in your DDR4 kit were binned and matched (and programmed) to work together.
"All opinions are not equal. Some are a very great deal more robust, sophisticated and well supported in logic and argument than others." - Douglas Adams

[/Korth]

I disagree with your statement about filling in all 4 Ram slots.

First of all.....If the CPU supports quad channels, like the x99 CPU's, you will fill in all memory slots with quad channel RAM. Intel's CPU's like the I3, I5. I7 and I9 series supports DUAL channel. And then it will be waste of money to buy quad channel RAM.

If you start with 2 sticks of 16GB in dual channel you don't need to worry about upgrading at a later time if you intend to go for 64GB in dual channels. You just buy another set of the same dual channel RAM. Remember you don't run in quad channels but in dual channels. That's why most motherboards have coloured memory slots....(2 grey and 2 black slots) or printed on the board close to the memory slots.

If you want to fill all 4 memory slots you must use 2x2 dual channel memory sticks....NOT quad channel memory sticks .If you do, you will get all kind of issues with BSOD and reboots.

Zka17
Level 16
LOL, this was a very odd discussion... but the advice stands: DO NOT MIX DIFFERENT MEMORY KITS!
There no such thing as buying "another set of the same dual channel RAM" - as described above, no two sets of RAM are identical when it comes to their very detailed specs (beyond of what you can see on their sticker).

However, you can play the lottery and try mixing... who knows, you may get lucky...

The basic idea is to give an advice which most likely will work, and that is: get a kit from your motherboard's manufacturer's QVL, and just double check with the RAM's manufacturer QVL.*