Why does QVL Sheet say different Dimms Support different amount of Slots?

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Carbongrip

Carbongrip

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Dec 21, 2015
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Hello everyone,

I don't typically follow the QVL sheet but with Ram prices being so inflated I decided to follow it a bit more closely. I have the Asus WS X299 Sage motherboard and I want to get DDR4 2666mhz ram sticks in black without heatsink.
I was looking at these,
https://www.newegg.com/Product/Product.aspx?Item=N82E16820236256
but according to the QVL sheet only 4 dimms are supported with this RAM. Why? It's JEDEC standard ram at stock X299 speeds.

If anyone knows why this is please comment, also if you have ram suggestions for black without heatsink dimms.

Cheers!
 
Solution
jojesa
Because the 8 DIMM configuration is not listed, it doesn't automatically means that it won't work. It is just that they have not tested that specific configuration.
If you are adventurous, you could see if it will work.
It will be close to impossible for motherboard manufacturers to test each module on all possible configurations.
So they post kits that have tested by them or memory manufacturer.
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jojesa

jojesa

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Dec 6, 2006
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A QVL list kits of dual and quad channels that have been tested to work together.
The single modules might not run in quad channel configuration.
To populate all the slots and run a quad channel configuration you get 1 kit like the Corsair 64GB (8x 8GB) CMK64GX4M8X4200C19 kit.
Also tyou could get wo kits of 4x 4GB or two kits of 4x 8GB, or two kits of 4x 16GB.
Ram kits are tested to work together in dual or quad channel configurations.
If you buy single modules (not from a kit) to run in quad channels, it's not guaranteed that it will work.
You could also look the memory QVL from manufacturer websites.
 
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photonboy

photonboy

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Jun 20, 2006
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The main reason you MAY have some issues is because the exact same model of memory may be made slightly different when run in different manufacturing batches.

If you buy a x4 DDR4 kit now the another "identical" kit later it likely will work fine but also may have some weird glitch where XMP doesn't work or something.

In the worst-case scenario usually you can manually adjust timings if something isn't quite working. I remember looking closely and saw at least one TIMING value was different. Probably due to the sourcing of the memory chips they received (possibly a different vendor).

In my case I got 2x4GB then a year later another 2x4GB of the exact same model. It actually applied XMP but then reported the incorrect frequency in Windows when I added the 2nd kit... however I tested the bandwidth and it was performing properly.

So...
As said it's recommended to buy everything you need in one bundle, but again chances are it will work fine with or without some tweaking if you do not and buy the same model later.
 
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photonboy

photonboy

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Other:
1) **CAS still matters a lot. I saw an "18" value which is pretty high. It also depends what CPU you have of course

If you go Quad Channel you can get away with lower frequency so 2400MHz might be fine (I'd still research) but I'd concentrate more on keeping the CAS down.

*make sure it is setup (see motherboard manual) as quad-channel then test with MEMTEST86 www.memtest86.com

2) not sure what they mean by only x4 DIMMS supported but I'm pretty sure that's not true

3) THIS (without knowing CPU) might be good quad-channel memory. It's 2400MHz CAS15, 4x8GB DDR4:
https://ca.pcpartpicker.com/product/bhtWGX/corsair-memory-cmk32gx4m4a2400c16
 
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photonboy

photonboy

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https://rog.asus.com/forum/showthread.php?96258-Testing-The-Impact-Of-Ultra-High-Speed-Memory-On-X299-Performance

This was for the 10C/20T CPU... they tested DDR4 2666MHz CL15 vs 4133MHz CL19 in a QUAD CHANNEL configuration (so 2x the available bandwidth vs dual-channel with same sticks)

Higher frequency is better.
Lower CAS (CL) is better.

They report overall that while the higher frequency kit did better overall that's mostly in SYNTHETIC tests. The 2666MHz CL15 kit (in Quad-Channel not Dual) was about the same for real-world testing.

So if you have a 10-core or lower CPU then a budget kit like I suggested of 2400MHz CL15 should be okay.

Do not go dual-channel.
Do not go too high with the CAS (CL) value when the frequency is low.
 
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Carbongrip

Carbongrip

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I will refine my question,

Why does the QVL list dimms as not being able to populate all 8 dimm slots? See below image,
y4mQC13at6GDOIJBHaX4-6gPv412YlLwsIIMyDjx5HFq2zyK1zo2lJDnYvQgdmu5HE5E53LDBTrF8YK-7SxBkKbU8hDPio6rLOS7l0xA31AbWU4wM490Zy-2f-Zo3yVu0xLehi-sSs35vlWyd23NRIuLZnPXOUk6IrHvOOpZH_S3IOJObqbwVlhAyRWKjSDe3fIyeZnczhr4C9uVr3tzQsYQQ


Also here is the full QVL for the Asus WS X299 Sage:
http://dlcdnet.asus.com/pub/ASUS/mb/Socket2066/WS_X299_SAGE/QVL/WS_X299_SAGE_Memory_AVL_20180702.pdf?_ga=2.139249971.1864202781.1533252645-176119893.1528181477
 
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jojesa

jojesa

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Dec 6, 2006
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Because the 8 DIMM configuration is not listed, it doesn't automatically means that it won't work. It is just that they have not tested that specific configuration.
If you are adventurous, you could see if it will work.
It will be close to impossible for motherboard manufacturers to test each module on all possible configurations.
So they post kits that have tested by them or memory manufacturer.
 
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Solution
Carbongrip

Carbongrip

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Dec 21, 2015
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Ah I was taking the list as they tested 8 dimms with those kits and it didn't work. I got it now. I think I will go back to ignoring the QVL sheets like I have always done, hasn't failed me yet. I can always manually tune it, I don't need XMP to work.
 
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P

Pinhedd

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Aug 7, 2007
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This is the correct answer.

QVL lists are nothing more than a list of what the motherboard manufacturer has tested in their quality control lab. It is not an exhaustive list.
 
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