Memory compatibility QVL vs reality

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fabio.lanza

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Apr 24, 2018
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Hi,

I have the Asus Crosshair VII Hero mobo and the QVL mentions that the memory CMR16GX4M2C3466C16 (2 kits = 32GB) can be run at 3000. I currently have it running at 2800 and it is still unstable. The PC resets automatically sometimes (not that frequent, but it happens).

When I use the auto clock settings in the BIOS, it boots with 2133Mhz. Should I take that as the stable speed?

Is there any tunning that I can do in the memory to have it stable at 3000Mhz as mentioned in the QVL? There are so many tunning options in the mobo, I have no idea. So far I did not to anything.

I have a Ryzen 2700X.


Thanks,

Fabio
 
Solution
Karadjgne
Quad channel vrs 2x dual channel is an ongoing question. While on the one hand, true quad channel ram has double the bandwidth of 2x dual channel ram, there's very little (if any) apps that'll actually take advantage of it. The only real advantage therefore is the fact that it's 4 sticks in a single kit, so guaranteed compatability from the factory.
However. If 1 stick goes down, for any reason, you are done. Replace all 4 sticks. You will not find a matching single quad channel ram stick anywhere.
Dual channel is everywhere. You can easily replace any 1 stick at any time. Or even 2x sticks. Without issue, just mix and match or fine tune till you get compatibility. With dual channel, options are open for any direction, with quad...
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fabio.lanza

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QVL says it is stable at 1.35V. On my mobo I see that memory voltage is set to 1.2V. Could this be the reason? What are the odds that I will burn the memory?

Thanks
 
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Karadjgne

Karadjgne

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You have 3466 Cas16 ddr4 ram. That means since it's ddr4, the base default speed will be 2133MHz. It's the same for almost any ddr4. In the bios, you'll also find under ram that it has different settings, such as XMP #1 or sometimes #2 and #3. These are preprogrammed settings from the ram, not the bios or pc.

So simply set XMP for a profile. The reason you are getting instability is because your numbers in the timings are not lining up with what the ram sees a normal. There's not only the Primary timings, which is the C16-17-16-38 T1 bit close to 40 other Secondary and Tertiary timings you aren't seeing. By just setting the speed as low as you are, you might as well be sticking a sock in a carburetor and considering that as saving gas. Doesn't work like that.

QVL is Qualified Vendors List. It simply is a list of what ram has been tested and the mobo vendor says it works. It's not a list of your particular ram run at different speeds. You have 3466MHZ capable ram. It's different than the QVL having a listing for 3000MHz ram or 2800MHz ram.

The ram has a title. The mobo has limits. Some mobo's will only accept (for instance) upto 3200 ram. What happens then is if the ram is recognised, it'll run at 3200 or it won't be recognised. But if you stick 3200 ram in there, no issues, even if oc'd upto 4000, because the ram is still 3200 titled.

You have 2x kits. 1 kit should be in 1-3 slots, the other kit in 2-4 slots. This is best for compatability. If there's any incompatability, which is quite possible, you can change some settings in the bios. Sometimes it's add a little voltage to SA Agent, sometimes it's add a little OC to the cpu, sometimes it's relax the primary timings. There's no set switch, there's no auto anything that'll fix incompatible ram. Just trial and error.

Best bet is to enable XMP profile for 3466 and leave it, if it's still unstable, then worry about other settings, any of which are explained in your mobo user manual.
 
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fabio.lanza

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Apr 24, 2018
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Thank you for the detailed answer. I have some follow-up questions if you can please take a look I would really appreciate.

QVL actually points out memory: CMR32GX4M4C3000C15(Ver3.32)(XMP) and mine is 2 kits of CMR16GX4M2C3466C16. I am not an expert but I thought that if I had a faster memory I should be able to run it at a lower speed just fine. I don't quite understand all the technical differences between the memory in the QVL and the one I purchased. Perhaps I should have pick exactly what is the QVL.

What I did in the BIOS now was, selecting ODCP, then the 3466Mhz profile, and then bringing down frequency to 3000Mhz (it booted, now need to see if it is stable), as it did not boot at 3466Mhz.

Any change I might be putting the hardware at risk?

Other question... since I have 2 kits, I don't necessarily remember of making sure that I installed first kit on 1 and 3, and then second kit on 2 and 4 slots. I thought that since sticks were all the same it would not matter. Is it important that I review this?

Thanks again
 
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smashjohn

smashjohn

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Aug 14, 2017
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You need to set everything to match the RAM specs, timings, MHz, and voltages. If it says it’s spec’d at 1.35V, then you need to set it to 1.35 to get those timings and speeds to work.

Also remember you’re running ddr memory so you set your memory speed (MHz) to half the spec’d data rate.
 
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Karadjgne

Karadjgne

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To figure out what ram is in what kit, you'll need to look at the serial numbers. On the sticker will be that long CMR16GX4M2C3466C16 - xxxxx etc. Those xx's are the actual number of that particular ram stick. So if you have 12345,12347,23456,23457 then the first 2 will be from the same batch and the second 2 from a different batch. That's where any incompatible ram comes from, different batches of silicon that the chipsets are made from. The first batch of numbers is the model.
CMR16GX4M2C3466C16
CM Corsair Memory
R RGB
16 16Gb kit.
GX Vengeance
4 DDR4
M2C dual channel ram
3466 ram speed rated under XMP profile
C16 primary Cas timing series.
Then the serial codes.

That's your ram.

CMR32GX4M4C3000C15 is totally different. That's a ddr4 3000 32Gb RGB kit with 4x8Gb quad channel (4C) sticks at Cas15. Whole different setup. You can't guage your ram based on its setup as those are 4sticks specially picked and set at the factory to work together. Yours aren't. Yours is 2x sticks.

For correct timings for your ram at less than rated speed, run cpu-z and look at the jadec table. (it'll show single data rate, so double it for ddr), so for 2800 you'd look at 1400MHz. Because you are running all 4 sticks, I'd leave the vram higher at 1.3v instead of the normal 1.2v
 
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fabio.lanza

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Apr 24, 2018
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Thanks for the additiona linformation. To conclude, I can still return both kits. Do you think it would be better to retun them and buy the CMR32GX4M4C3000C15 instead?

Thanks
 
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fabio.lanza

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Apr 24, 2018
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Thanks for your answer, I did, stable so far, monitoring. Thanks.
 
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Karadjgne

Karadjgne

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Quad channel vrs 2x dual channel is an ongoing question. While on the one hand, true quad channel ram has double the bandwidth of 2x dual channel ram, there's very little (if any) apps that'll actually take advantage of it. The only real advantage therefore is the fact that it's 4 sticks in a single kit, so guaranteed compatability from the factory.
However. If 1 stick goes down, for any reason, you are done. Replace all 4 sticks. You will not find a matching single quad channel ram stick anywhere.
Dual channel is everywhere. You can easily replace any 1 stick at any time. Or even 2x sticks. Without issue, just mix and match or fine tune till you get compatibility. With dual channel, options are open for any direction, with quad channel you are locked in what you have.

All that said, you have an Asus ROG X470 Crosshair VII Hero. That's AM4. It'll only support dual channel ram. You'd need a TR4/x299 for quad channel support. You can't use quad channel ram on a dual channel mobo.
 
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