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DDR4 rank for Ryzen, help me understand

JimKiler

Diamond Member
Oct 10, 2002
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i never heard of rank for RAM but on anandtech they show


So in a simple form after searching google if a RAM chip has memory of both sides it is dual rank and if it is on one side it is single rank? Do i have that correct?
 

Dasa2

Senior member
Nov 22, 2014
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as far as i know all 16g sticks are dual rank \ double sided
most old 8g sticks and some new are also dual
 

JimKiler

Diamond Member
Oct 10, 2002
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it should be interesting to see how much rank causing slower RAM bandwidths will make for Ryzen.
 

roybotnik

Junior Member
Mar 4, 2017
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Best to check the manufacturer site. Technically single rank dimms can have chips on both sides. Not sure if that is seen in practice.

I am using dual rank dimms with my 1800x, and can't achieve speeds above 2666 so far. My sticks are gskill tridentz 16gb x2, rated 3200C14. However it seems that my memory latency is a little low than what I have seen in benchmarks, at around 85ns.

Going to hold onto this stuff for a little bit to see if BIOS updates will fix compatibility, if not I might have to return and go with 8gb x2.

(Spam removed)
 
May 11, 2008
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That is very informative. Thank you.
I should note that with freeware cpu-z , the spd can also be read and the rank setup determined.

http://www.cpuid.com/softwares/cpu-z.html

Required by a potential ryzen buyer :
Two identical (at least 4GB) ddr4 modules with a single rank memory module for each.
At least 2667 DDR4 and preferably with timings that actually work on the voltage that is the default DDR4 voltage (1.2V).
 
Last edited:

tcsenter

Lifer
Sep 7, 2001
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"Rank" is technically not synonymous to chips being on either (or both) physical sides of the module board. There can be single-rank DIMMs with chips on both sides. But it usually (not by definition) works out that if a module is double-rank, it will have chips on both sides, or if single-rank then chips only on one side.

To better understand what is meant by a DIMM rank, it may be helpful to remember that the PC memory bus is 64-bits wide (or 72-bits for ECC). The module (and chips) must be wired-up in such a way so that only a certain combination or set of chips will be 'actively' connected to the memory controller at any given time in order to create this 64-bit wide area (a.k.a. row).

The term DIMM side, or "rank" as it is now called by JEDEC, refers to this particular combination of chips that will create a full 64-bit read or write over the memory bus at any given time. Each DIMM can have one or two ranks (modules designed for servers can have four ranks). Each 64-bit rank is connected to a circuit in the memory controller called a Chip Select (CS). The number of independent CS signals supported by the memory controller defines how many ranks are supported. Current memory controllers typically have a total of eight CS signals, supporting a total of eight 64-bit ranks (server chipsets are coming with more).
 
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TemjinGold

Diamond Member
Dec 16, 2006
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So am I correct to think that currently, me having dual rank memory hurts me but when this whole bios thing is fixed, I will be better off than people with single rank?
 

fleshconsumed

Diamond Member
Feb 21, 2002
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Another question to throw, if I'm going to do a Ryzen build I'll probably go with ECC ram. I see quad rank ECC ram on ebay. Does anybody know if Ryzen platform, i.e. CPU and motherboards support quad rank RAM?
 

Malogeek

Golden Member
Mar 5, 2017
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yaktribe.org
Does anybody know if Ryzen platform, i.e. CPU and motherboards support quad rank RAM?
They all support 4 DIMMs just not at high speeds. Depending on the DIMMs and the final size, you'll be limited to 2133 or 1866 likely. It looks like the ASRock Taichi supports ECC RAM.

Ryzen itself supports ECC of course.
 

fleshconsumed

Diamond Member
Feb 21, 2002
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They all support 4 DIMMs just not at high speeds. Depending on the DIMMs and the final size, you'll be limited to 2133 or 1866 likely. It looks like the ASRock Taichi supports ECC RAM.

Ryzen itself supports ECC of course.
Please note that I said "quad rank" modules, this is not the same as 4 dimms at once :)
 

sdifox

No Lifer
Sep 30, 2005
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Another question to throw, if I'm going to do a Ryzen build I'll probably go with ECC ram. I see quad rank ECC ram on ebay. Does anybody know if Ryzen platform, i.e. CPU and motherboards support quad rank RAM?
I don't think Ryzen does quad rank ecc at all. It's a desktop chip, maybe the server version will.
 

guachi

Senior member
Nov 16, 2010
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So am I correct to think that currently, me having dual rank memory hurts me but when this whole bios thing is fixed, I will be better off than people with single rank?
I don't believe so. You'll only be better off in that you can get 2x the memory on dual rank as single rank. The fastest dual rank memory I've seen for Ryzen that's verified on a QVL list is 2400. If that's fast enough for you AND you want at least 32 GB get dual rank.

If 16 GB is enough for you I'd get get the fastest pair of 8 GB sticks of RAM that you're comfortable paying for as the prices rise fairly quickly for faster RAM/better timings.
 

TemjinGold

Diamond Member
Dec 16, 2006
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I don't believe so. You'll only be better off in that you can get 2x the memory on dual rank as single rank. The fastest dual rank memory I've seen for Ryzen that's verified on a QVL list is 2400. If that's fast enough for you AND you want at least 32 GB get dual rank.

If 16 GB is enough for you I'd get get the fastest pair of 8 GB sticks of RAM that you're comfortable paying for as the prices rise fairly quickly for faster RAM/better timings.
That's right now. I mean when they sort this out.
 

DuronBurgerMan

Junior Member
Mar 13, 2017
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I ran 32GB of dual rank RAM (two DIMMs) at 2933 16-16-16-36 on my Asus X370 Prime... until the Agesa 1004 update. Now I'm back to 2400 at 15-15-15-35, and I can't get the 2666 or 2933 dividers to post. Strangely, the machine still benchmarks 2-3% higher in everything, despite the slower RAM speed. So the 1004 update came with some performance boosts somewhere.

But I want my RAM back up at 2933, damnit.
 

Malogeek

Golden Member
Mar 5, 2017
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I ran 32GB of dual rank RAM (two DIMMs) at 2933 16-16-16-36 on my Asus X370 Prime... until the Agesa 1004 update. Now I'm back to 2400 at 15-15-15-35, and I can't get the 2666 or 2933 dividers to post. Strangely, the machine still benchmarks 2-3% higher in everything, despite the slower RAM speed. So the 1004 update came with some performance boosts somewhere.
A lot of other X370 Prime users in the same boat. I can't do anything above 2400 either on 0604.
 

Rifter

Lifer
Oct 9, 1999
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I ran 32GB of dual rank RAM (two DIMMs) at 2933 16-16-16-36 on my Asus X370 Prime... until the Agesa 1004 update. Now I'm back to 2400 at 15-15-15-35, and I can't get the 2666 or 2933 dividers to post. Strangely, the machine still benchmarks 2-3% higher in everything, despite the slower RAM speed. So the 1004 update came with some performance boosts somewhere.

But I want my RAM back up at 2933, damnit.
I had my ram at 3000(2933) on 515 but when i upgraded to 604 it wouldn't post even at 2400, 2133 is the best i could do even when ramming 1.1V into the SOC and 1.35v into the ram at CL 18 timings, it was ridicules, i was actually laughing by the end of it as i started at 2933 and then worked my way all the way down to 2133 before it would boot.... I dont think it took me longer than 5 min to say screw it and went back to 515. Obviously 604 is not ready for prime time this bios never should have been released, and to say it improved memory compatibility was just laughable.
 

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