Single-Rank vs Dual-Rank

[Nebulous]

Can't believe a small issue like that will prove to be a real problem. I've been running 4 sticks (4x16gb) in my rig since day one, but then I started getting random issues like stuttering while gaming and every once in a while the rig will get stuck on stupid.

I'm playing the 'ol switch-a-roo with sticks in different slots and memtest. Mem slots are working correctly and each stick passed memtest. I'm stuck scratching my noggin' wondering why this keeps happening.

Decided to get another set of GSkill Ripjaws V , since the memory I already have was purchased from the same place.

So I get the new ram in and recheck, all good.....except for one slight little bugger called "RANK". Come to find out I overlooked the fact that memory came in single rank and dual rank.

My 2 sets were split:
One set was single rank and the other was dual rank. All this time this is what was causing my little naggin' problem. I can't believe I missed that I made sure the timings and voltages are identical in both sets, but didn't think they would come in different ranks.

3rd set I got was dual-rank, so I removed the single-rank set and made sure all 4 sticks are dual rank. Still too early to tell, but the rig is running normally. I even tightned the timings to cas 16 and still rocking steady.

Be sure when you buy ram, don't mix ranks. Keep Single-Rank single, and Dual-Rank dual. Hope this make sense.

 

[mackerel]

To the best of my understanding:

DDR4
4GB modules - all single rank?
8GB modules - could be dual rank from like 2015, but anything recent will be single rank. Or even worse: 1Rx16. I think enthusiast stuff is ok at 1Rx8. 1Rx16 is more a risk for OEM boxes and laptops.
16GB modules - were dual rank early on, moving to single rank in recent years.
32GB modules - probably dual rank

DDR5
8GB modules - probably 1Rx16 - avoid
16GB modules - probably 1Rx8 - ok
32GB modules - probably 2R - nice

As chip density increases things tend towards lower ranks. When upgrading my laptop, it took quite some digging to ensure I got the better 2R 16GB DDR4 modules as opposed to 1R which was more common then. When building my current desktop I went to 2x32GB DDR5 to get 2R. I never actually verified that. I bought a same kit of 2x16GB which should be 1R in order to test the difference. I still haven't done that. Anyone want to place bets if it'll happen this year or not?

 

[Woomack]

You can mix single and dual rank kits, but in general it's better to use a single-rank kit in first slots. Also, a worse speed/profile should be installed in the first slots. What's more, lower-capacity modules should be installed in the first slots. This can cause problems as dual-rank usually has higher capacity and lower speed (kits at the same frequency and main timings have worse secondary timings).
Some brands use different product numbers if there are any IC differences, while others keep the same product numbers for various ICs, ranks, etc.

With DDR4, it highly depends on the IC manufacturer:
Samsung - 4/8GB modules = single-rank, 16GB only dual-rank, no 32GB modules in gaming/consumer kits
Hynix - 4/8GB = single-rank, 16GB single or dual rank (latest series only single), 32GB dual-rank
Micron - 4/8GB = single rank, 16GB single or dual rank (the same as Hynix, older kits dual, newer single), 32GB dual-rank

DDR5 in popular kits from well-known brands is like 16/24GB = single-rank, 32/48GB = dual-rank ... there is, however, an exception as there are new dual-rank Hynix 2x16GB kits (look at the KLEVV FIT V I reviewed recently). Now, since Samsung does not exist in any popular DDR5 consumer/gaming kits, then it's easier to tell what is under heatsinks in new kits. Micron is used only in low-speed, budget series and everything from Crucial, so 90%+ of popular kits use Hynix A/M (5600->9000+). Introduced recently, CUDIMM (except the basic series with only JEDEC speeds) uses only Hynix A/M, too, and a clock driver.

 

[mackerel]

Here's my DDR4 8GB 2R module from a long time ago. Don't expect to find them now but they did exist back then.

 

[Nebulous]

Here's my dual rank in my rig.


And the single rank that was in my rig, is now in my son's rig



When I was running both single & dual rank at the same time, I can only run XMP or manual stock timings. Nothing past that would work. But each set solo had no problems getting them to run alittle faster in terms of speed (3733 and C16). Nothing beyond that tho.

 

[freeagent]

I honestly feel no need to upgrade my platform other than FOMO, but really.. that isnt a big deal.

From 1155 to AM4.. I am seeing a slow pattern here