RAM questions - LRDIMM vs RDIMM, Hynix brand, and mixing different sizes (same speed and type though

Notice: Page may contain affiliate links for which we may earn a small commission through services like Amazon Affiliates or Skimlinks.

HotFix

Member
May 20, 2015
87
23
8
Silver Spring MD
blogs.technet.com
Hey guys,
I posted at the bottom of another motherboard vs thread and I think it will get buried there as it is a different topic. Also I hope this is the right spot for a RAM question as I didn't see a forum for RAM so motherboards seemed like the logical place.

First question.
Is LRDIMM better/worse than RDIMM in DDR4? I did a bunch of searching online but most articles talk about the difference in DDR3, and I understand that the DDR4 versions of these are different/better. I do understand that LDRIMM allows you to go higher density, but beyond that I'm not clear if there is a performance hit with LDRIMM or if there is another reason to avoid it.

I also came across a good deal on some Hynix DDR4 ECC ram on Ebay but I'm not familiar with this brand. It seems like Samsung is the gold standard on these forums, but does anyone have any experience with using Hynix memory? Supermicro certified it for the motherboard I am leaning towards but since I don't know how popular this brand is I am worried about buying sticks now on a good deal, and in the future not being able to find it at a reasonable price (due to its potential unpopularity) when I want to add more.

Also last tangential question - if I put in 4 x 16GB sticks now, will I have issues in the future if I put in 4 x 32GB sticks even if they are the same speed and rating. I understand from Supermicro's motherboard manual that speed and type have to match, but it seemed like size could change. I have done this in HP ProLiant servers in the past w/o issue, but that isn't necessarily an apples to apples comparison.

Thanks all!!!
 

neo

Well-Known Member
Mar 18, 2015
672
363
63
In simple layman's terms, DDR4 LRDIMM (load reduced memory module) has an extra chip on stick which provides I/O buffers, increases capacity capability, increases signal integrity and offloads some memory functions from Intel's Memory controller. It is the next technological standard which will be replacing RDIMM. Whether you technically need it, is a matter of opinion and requirement. To answer your question directly, there are no reasons to avoid it besides possibly it's price if you are on a budget.

If you are curious what it looks like, I posted a photo of LRDRIMM stick in my build thread recently.


Hynix memory is fine, most people don't realize it but it is also a Korean brand - just like Samsung. It is actually a renamed semiconductor subsidiary of Hyundai which is the largest conglomerate of Korea. They been spinning silicon since the 80's. Comparing Hynix to Samsung would be a personal preference if your motherboard manufacture certified them both. If you want to be picky, compare the speed, timings and obviously price.
 
Last edited:
  • Like
Reactions: HotFix

T_Minus

Build. Break. Fix. Repeat
Feb 15, 2015
7,625
2,043
113
Samsung and Hynix are in most of my SuperMicro boards, FWIW they both work great :)
 
  • Like
Reactions: HotFix

HotFix

Member
May 20, 2015
87
23
8
Silver Spring MD
blogs.technet.com
Thanks guys. You waylaid my fears of Hynix (I used Hyundai memory occasionally in the old days w/o issue). I think 16GB DDR4 ECC for $140 is a great deal then.

Any thoughts of mixing RAM modules of different sizes but the same speed and rating? I would only do this between channels, not within a channel. For example this motherboard appears to have 4 channels of memory:
Supermicro | Products | Motherboards | Xeon® Boards | X10SRH-CLN4F
I would populate channels A & B with 4 identical 16GB RDIMMs, but maybe in the future use 32GB RDIMMS in channels C & D.
 

T_Minus

Build. Break. Fix. Repeat
Feb 15, 2015
7,625
2,043
113
I've had no problem mixing memory (DDR3) like you just mentioned.
 
  • Like
Reactions: HotFix

T_Minus

Build. Break. Fix. Repeat
Feb 15, 2015
7,625
2,043
113
I've done some crazy mixing just to test RAM, and I've been surprised it works practically every time.
 

herby

Active Member
Aug 18, 2013
187
53
28
I've done some crazy mixing just to test RAM, and I've been surprised it works practically every time.
I've done a little mixing myself (cas, frequency, even voltage) and not noticed a problem.

As I understand it modern RAM will present profiles of the timing, speed, and voltage in which it can run. The motherboard will then choose the best common denominator. For example I have some 1.3v ram that runs just fine at 1.5v, or a pair of DDR3 1600 CAS 9 DIMMS that's at 1333 CAS 9 to match the pair in the other channel.

You might be able to dig up some datasheets that'll confirm that all the RAM you're looking at have overlapping profiles but I wouldn't worry about it too much.
 
  • Like
Reactions: T_Minus

mrkrad

Well-Known Member
Oct 13, 2012
1,244
52
48
Be careful with quad-rank 16gb dimms, you might run out of rank before you run out of slots! And Hyperdimm/LRDIMM cannot be mixed with conventional dimms!
 

Patrick

Administrator
Staff member
Dec 21, 2010
12,511
5,792
113
And if you want to get really excited, Hynix is actually SK Hynix and you can guess what the SK stands for.

Certainly a top tier manufacturer. They run their own fabs just like a Micron or a Samsung on the RAM side and are actually starting to get into more higher-end NAND and logic manufacturing.
 

HotFix

Member
May 20, 2015
87
23
8
Silver Spring MD
blogs.technet.com
And if you want to get really excited, Hynix is actually SK Hynix and you can guess what the SK stands for.

Certainly a top tier manufacturer. They run their own fabs just like a Micron or a Samsung on the RAM side and are actually starting to get into more higher-end NAND and logic manufacturing.
I feel like such a dunce on this site. :)

SK = Super Kool?

In all seriousness neither NY wife or I figured this one out and you got me a little nervous since I just purchased 4 of the Hynix 16GB RDIMMs.
 

ATS

Member
Mar 9, 2015
96
32
18
48
Thanks guys. You waylaid my fears of Hynix (I used Hyundai memory occasionally in the old days w/o issue). I think 16GB DDR4 ECC for $140 is a great deal then.

Any thoughts of mixing RAM modules of different sizes but the same speed and rating? I would only do this between channels, not within a channel. For example this motherboard appears to have 4 channels of memory:
Supermicro | Products | Motherboards | Xeon® Boards | X10SRH-CLN4F
I would populate channels A & B with 4 identical 16GB RDIMMs, but maybe in the future use 32GB RDIMMS in channels C & D.
Just an FYI, you are going to want the same capacity in each channel for optimal performance. So instead of doing 2x16GB in A&B and 2x32 in C&D, you are better off doing 16GB+32GB in each channel. So initially you'll want to do 1x16GB in each channel. If you want to later buy 2 32GB dimms, you should be able to do 2x16 in A&B and 1x32 in C&D but its probably not recommended (its likely going to be an untested config or a config that has received minimal testing though in theory it should work).
 

trumee

Member
Jan 31, 2016
222
12
18
54
Be careful with quad-rank 16gb dimms, you might run out of rank before you run out of slots! And Hyperdimm/LRDIMM cannot be mixed with conventional dimms!
Please can you elaborate on this. The 32GB LRDIMM compatible memory listed for my motherboard is all 4R. On the other hand the 16GB module is 2R. Is one better over another?
 

Evan

Well-Known Member
Jan 6, 2016
3,346
598
113
I have always seen only 3 Brand’s used by the major manufacturers of servers recently..
SK Hynix, Samsung, Micron
And of course they all work together in the same server no issues, what I do find interesting is the SK Hynix memory can come from Korea or china, the Korea version must be a smaller manufacturing node and large size chips as the number of chips is a lot less and smaller for the same size. I could take photos of 5 or 6 different 16gb dimm and you would be surprised how different they all look. (All rated the same size and speed etc and work together)