RAM explained: Why two modules are better than four / single vs. dual-rank / stability testing

[Doc_Bucket]

In WinRAR bench, i usually see pretty quickly if a run is quite "underwhelming" because of some background load, then i abort it and start it again (often a couple times) until i get numbers that make sense. If you want to average the numbers, it would be best to exclude the runs which are clearly too low because of something else going on. However, a 40 points difference at such a high amount of points, if you translate that into a percentage, it's almost nothing. If we then also apply a margin of error, these two setups result in an equal RAM performance, so i would choose the one that the memory system is more comfortable with (less voltage and better RTLs/IOLs).

Yes, I have the same feeling. I have to go by intuition to a certain degree, that's what I've learnt this time.
In any case, this thread is blessed with your knowledge and experience, it makes things possible.

 

[Doc_Bucket]

A couple of final observations.

1) If you have problems running Ubuntu under Win 11, try to install "Windows Subsystem for Linux Preview" first and carry out the installation from a command line there. Enabling WSL, HyperV and Virtual Machine in Control Panel might not be enough.

The next trouble is Intel XTU vs. Virtual Machine. You cannot run both at the same time. I had to run GSAT with CPU at stock values, I hope it counts as a valid test. CPU did not seem to be stressed at all, except for IMC voltages. But even with that, Prime95 pushed the readings of VCCIO/VCCSA in HWiNFO64 yet slightly higher. My impression is Prime95 is stressful on CPU in all respects, no matter what. GSAT focuses on RAM, but as I say, it is probably not quite accurate to compare stock and overclocked behaviour of the CPU. It depends on what GSAT exactly does, which I do not know.

2) For the sake of methodology: after finding out about weaknesses of HCI MemTest 7.0 I did all my testing in OCCT and Prime95. The latest first error in OCCT occurred at 42:19! This is well past the 30 minutes minimum suggested by MemTestHelper Guide (see links above). I have carried out a few dozens of tests with both SSE and AVX in OCCT with the duration of up to 1 hour. As the RAM overclock passed a 2 hour test in GSAT in the end, I'd say 60 minutes in OCCT should be enough in most cases and 45 min is a slightly risky minimum. All major errors will practically show within 5-15 minutes, but those teetering on the edge take longer.

 

[CtrlAltDeluxe]

3) Amount of RAM

32 or 64 GB RAM can be justified for large video editing projects, rendering, heavy photoshop use and such cases. But if it's gaming for example, modern games very rarely use more than 16 GB RAM. There are just the first games coming out, like Flight Simulator 2020, who will use a little more than 16 GB RAM, but still basically run at the same speed. So, 32 GB would definitely be a generous amount, but it can be befitting for a high-end gaming system.
16 GB RAM: Use 2x 8 GB (good mid-range / gaming systems, most of the time you won't need more.)
32 GB RAM: Use 2x 16 GB (high-end gaming systems - when all other bottlenecks are removed - and uses beyond gaming, such as video processing etc.)



3b) How to increase the RAM size when you have 2x 4 GB or 2x 8 GB RAM?

First choice: Replace the 2x 4 GB with 2x 8 GB, or the 2x 8 GB with 2x16 GB. The new RAM should be a kit of matched modules. This will ensure the best performance and the least problems, because there's only two modules again in the end.

Second choice: Add a kit of two matching modules to your two existing modules. But you might not be able to get the same modules again. Even if they are the same model, something internally might have changed. Or you might toy with the idea of adding completely different modules (for example, adding 2x 8 GB to your existing 2x 4 GB). This can all cause problems. The least problems can be expected when you add two modules that are identical to your old ones. But then there's still this: You are now stressing the memory system more with four modules instead of two, so the attainable RAM frequency might drop a little. Also, it's electrically worse on a mainboard with daisy-chain layout, as explained under 1).

I've got 2x8 3600, cl16 (16, 20, 20, 40), with an i7 12700k. I didn't want to go with DDR5 as it's 3 times the price in my country, still. Then again, I also want to keep the system for at least another 5 years (got it in January). I've got a RTX 3070, gaming on an 1440p 165Hz monitor, so not looking to buy a new GPU until the RTX 5000 series.

The only upgrade that makes any sense is another 8 gigs of RAM, to get dual rank and 32 gb for future proofing.
Would that be a smart move, or would 4 DIMMs unnecessarily create problems in my system (daisy chain topology)?
Would I actually see any benefit long term or will 16 gb be enough for the next 5 years?

My use case is 90% gaming, with 10% going to MS Office, browsing...and maybe sometimes (though rarely) DaVinci Resolve.

I appreciate any advice you can give me, and thank you in advance.

 

[citay]

You have several options. In your case, i would stay at 2x 8 GB for now, and only upgrade when i need to. Right now the games that make use of more than 16 GB RAM are few and far between, and often they don't even run notably better from that. So unless that changes on a broader scale (and there are no signs of that yet, because of the focus on console game sales), there is no need to act yet.

When you upgrade, it depends if you can get the same exact kit of 2x 8GB again. Note that some RAM brands change the RAM underneath the heatspreader and keep selling it under the old model name. Or Corsair for example, they change the little "Ver.:" on the RAM, which means a different version of the same model, which again is not identical and cause problems for the memory system.

If you were to upgrade now, the positive thing of that is that you could probably get the exact same RAM kit again. But do you really need more than 16 GB in the next 5 years?
Hard to say for sure, it also depends if you also want to always play the latest AAA games. Maybe some landmark game will come out in that timespan that does run better at 32 GB. But for now they all do fine with 16 GB, even AAA games.

If you were to upgrade later, the exact same RAM kit might not be available anymore, so then i would go to 2x 16 GB and sell your old 2x 8 GB kit. So that would be the backup plan, if one or several games come out that run notably better with 32 GB.

 

[CtrlAltDeluxe]

You have several options. In your case, i would stay at 2x 8 GB for now, and only upgrade when i need to. Right now the games that make use of more than 16 GB RAM are few and far between, and often they don't even run notably better from that. So unless that changes on a broader scale (and there are no signs of that yet, because of the focus on console game sales), there is no need to act yet.

When you upgrade, it depends if you can get the same exact kit of 2x 8GB again. Note that some RAM brands change the RAM underneath the heatspreader and keep selling it under the old model name. Or Corsair for example, they change the little "Ver.:" on the RAM, which means a different version of the same model, which again is not identical and cause problems for the memory system.

If you were to upgrade now, the positive thing of that is that you could probably get the exact same RAM kit again. But do you really need more than 16 GB in the next 5 years?
Hard to say for sure, it also depends if you also want to always play the latest AAA games. Maybe some landmark game will come out in that timespan that does run better at 32 GB. But for now they all do fine with 16 GB, even AAA games.

If you were to upgrade later, the exact same RAM kit might not be available anymore, so then i would go to 2x 16 GB and sell your old 2x 8 GB kit. So that would be the backup plan, if one or several games come out that run notably better with 32 GB.

Thank you for your input.

However, you've given me both options again. Which one do you lean more towards?

I probably won't sell the memory for 2x16 or try to find the same kit again (which will probably be imposible) in a few years. It will be too much of a hassle. At that point I might as well suffer through performance loss until I upgrade cpu+mobo+ram.
If I'd see any benefit a few years down the line, or if there will be a big difference in fps or 1% lows now or in the future, I'd rather buy now than wait, since I can buy the exact same kit while it's still available. If not, I'd rather just forget about the RAM until my next CPU upgrade in 5 to 8 years.

Do I need it though? And will it really not cause any trouble, or just not that much?
Some people say dual rank adds 5 to 10% performance, others say it doesn't boost performance at all.
Some say 32gb is minimum and really help with 1% lows FPS (techdeals e.g.) others say it doesn't make a single difference.
Some say it adds unnecessary stress on the memory controller, especially having a daisy chain topology, potentially not being able to use XMP, others say it all works just fine.

Dunno what to do...

PS
The exact memory that I have is Kingston Fury 16GB Renegade DDR4 3600MHz CL16 KIT, model: KF436C16RBK2/16

 

[citay]

Eight years might be a bit of a stretch with 16 GB. As i said, hard to predict the future, but if there's a PS6 and next-gen Xbox by that time, they might come with 32 GB RAM and the games might slowly start to appreciate that, even on PC. So if we're talking eight years, and you don't want to get 2x 16 GB later, then you might as well get a second kit of that exact 2x8 one now.

As i write in the post, "Dual-rank is slightly faster performance-wise (up to 4%), but also loads the memory controller more." We can't really call this a "boost" of performance, you won't really notice it, but it is slightly faster. At DDR4-3600, we're not in the territory yet where four single-rank modules (which you would end up with, and which would mean something like a dual-rank operation for the memory system as a whole) cause a significant problem for the memory system. So the likelyhood of being able to use XMP without stability problems is pretty good.

 

[CtrlAltDeluxe]

Eight years might be a bit of a stretch with 16 GB. As i said, hard to predict the future, but if there's a PS6 and next-gen Xbox by that time, they might come with 32 GB RAM and the games might slowly start to appreciate that, even on PC. So if we're talking eight years, and you don't want to get 2x 16 GB later, then you might as well get a second kit of that exact 2x8 one now.

As i write in the post, "Dual-rank is slightly faster performance-wise (up to 4%), but also loads the memory controller more." We can't really call this a "boost" of performance, you won't really notice it, but it is slightly faster. At DDR4-3600, we're not in the territory yet where four single-rank modules (which you would end up with, and which would mean something like a dual-rank operation for the memory system as a whole) cause a significant problem for the memory system. So the likelyhood of being able to use XMP without stability problems is pretty good.

Thanks for the reply.

Well, 8 years tops...but then again, no one knows how CPUs will develop. My 12700k might last a decade, or just 3 years.

Though $115 for another 2x8 isn't much, I'd also rather not waste the money and start saving for an GPU down the line. No game recommends more than 16gb now, but like you said, who knows what the PS6 will do, and when...

I hesitate to buy mostly because of the original sentiment and headline, which makes perfect sense, that two modules are better than 4, and I'd hate to run into problems because of the daisy chain topology. But I'll trust you when you say I won't have any issues with xmp and stability.

 

[Doc_Bucket]

Thank you for your input.

However, you've given me both options again. Which one do you lean more towards?

I probably won't sell the memory for 2x16 or try to find the same kit again (which will probably be imposible) in a few years. It will be too much of a hassle. At that point I might as well suffer through performance loss until I upgrade cpu+mobo+ram.
If I'd see any benefit a few years down the line, or if there will be a big difference in fps or 1% lows now or in the future, I'd rather buy now than wait, since I can buy the exact same kit while it's still available. If not, I'd rather just forget about the RAM until my next CPU upgrade in 5 to 8 years.

Do I need it though? And will it really not cause any trouble, or just not that much?
Some people say dual rank adds 5 to 10% performance, others say it doesn't boost performance at all.
Some say 32gb is minimum and really help with 1% lows FPS (techdeals e.g.) others say it doesn't make a single difference.
Some say it adds unnecessary stress on the memory controller, especially having a daisy chain topology, potentially not being able to use XMP, others say it all works just fine.

Dunno what to do...

1) The chances are 2x16 GB of DDR4 RAM 3-4 years from now will not be that much more expensive than extra 2x8 GB of the same kit now, for DDR5 will be a mainstream.
Or,
2) You can get those 2 extra DIMMs now, not install them and wait until you really need more than 16GB of memory, if that moment really comes. Otherwise, as this thread shows, running 4x8 GB will worsen your performance.

It's a bet on the market behaviour, which always entails some amount of risk.

1% low FPS depend on how well CPU communicates with GPU, which also depends on the throughput of RAM:
{(2 channels x 2 (DDR) x actual clock (1800 in your case) x 64 (bits)) / 8} minus delay caused by latencies and timings = throughput in MB.
The size does not matter.

You would need both CPU and MoBo that support a quad channel traffic in order to make full advantage of 4 DIMMs without a loss. But that is not your case as I understand it.

Say, I am in a position similar to yours as a user. I do not think of buying extra 2x8 GB of RAM any time soon, lucky to have a better than average rig with just 16 GB. I am sure most game developers are aware of what an average rig is capable of and they have little intention to push the limits for that would mean fewer potential buyers. So as I see it an average user has an upper hand here and 16 GB of RAM will be enough in the foreseeable future. Or DIMMs will become so cheap that 16 or 32 GB will not make a substantial difference.

 

[CtrlAltDeluxe]

The chances are 2x16 GB of DDR4 RAM 3-4 years from now will not be that much more expensive than extra 2x8 GB of the same kit now, for DDR5 will be a mainstream. You can get those 2 extra DIMMs now, not install them and wait until you really need more than 16GB of memory, if that moment really comes. Otherwise, as this thread shows, running 4x8 GB will worsen your performance.

It's a bet on the market behaviour, which always entails some amount of risk.

1% low FPS depend on how well CPU communicates with GPU, which also depends on the throughput of RAM:
{(2 channels x 2 (DDR) x actual clock (1800 in your case) x 64 (bits)) / 8} minus delay caused by latencies and timings = throughput in MB.
The size does not matter.

You would need both CPU and MoBo that support a quad channel traffic in order to make full advantage of 4 DIMMs without a loss. But that is not your case as I understand it.

Are you sure about not being more expensive in 4 years? When DDR4 production is dropped the remaining modules will go up in price, it happened to DDR2 and DDR3.

I'm sorry, could you explain how running 4x8 will worsen my performance? I thought any stress on the memory controller will be compensated by running dual rank, and then some. I actually thought I'd get a 5 to 10% performance upgrade. Various Youtube videos show there's either a bit more performance (in 2 games a lot more), or none at all. I didn't see any performance degradation.'

Size doesn't matter in general or just 16gb vs 32gb?

I'm not sure, but I think my cpu and mobo support quad channel. I've got a 12700k and *cough* Asus TUF GAMING H670-PRO WIFI D4. There's a QVL list and there's even 4x32 RAM on that list. It does have a daisy chain topology though.

 

[citay]

I hesitate to buy mostly because of the original sentiment and headline

Well, it's "just" a headline and is differentiated further in the thread. While with DDR5, using four modules would be a bad idea no matter what, with DDR4 it depends.
The most difficulties will happen when you try to use four high-capacity dual-rank DDR4 modules. Then DDR4-3600 can definitely become quite challenging.
With four single-rank modules such as your 8GB ones would be, out of all the four-DIMM configurations, it's the mildest one, so DDR4-3600 should be possible.

The chances are 2x16 GB of DDR4 RAM 3-4 years from now will not be that much more expensive than extra 2x8 GB of the same kit now, for DDR5 will be a mainstream.

It's possible, but i wouldn't bet on it. Historically, RAM of previous generations doesn't nosedive in price. For example, 2x 8GB of decent DDR3 are still about as expensive as 2x 8GB of DDR4 now. Price for RAM is constantly falling at the moment, but that is just the hog/pork cycle, https://en.wikipedia.org/wiki/Pork_cycle
It can also increase again.

Otherwise, as this thread shows, running 4x8 GB will worsen your performance.

We need to be precise with the terminology. If the XMP still runs fine, than it can very slightly increase the performance actually (although that also depends on the workload, for example games tend to slightly prefer dual-rank, other things may see no benefit). Because now two single-rank modules per channel will effectively form a dual-rank configuration per channel. Of course, the stress on the memory system is higher with this configuration, and the XMP is never guaranteed per se. Although i'm somewhat optimistic that DDR4-3600 can still work well here. But if the XMP doesn't run and you have to make some sort of compromise in frequency or timings, then it would be true that it will worsen the performance.


edit, just seeing the reply:

I'm not sure, but I think my cpu and mobo support quad channel.

No. Quad-channel platforms have eight memory slots, always two slots per channel (except on the dual-channel RAM-overclocking-boards with just one slot per channel).

 

[CtrlAltDeluxe]

No. Quad-channel platforms have eight memory slots, always two slots per channel (except on the dual-channel RAM-overclocking-boards with just one slot per channel).

Oh, didn't know that, thanks.

Would manual OCing beyond 3600 (though potentially losing gear 1), or maybe tightening the secondary and tertiary timings be more beneficial than just slotting in another 2x8, set the xmp and call it a day?

 

[citay]

Doc_Bucket was correct in that when the game doesn't even utilize more than 16 GB (as most games wouldn't), then there is zero performance benefit from just the doubling of the RAM capacity. The performance increase from having more total RAM (not talking about the number of modules now) only comes into effect once something actually uses more RAM.

I would stay at DDR4-3600, and yes, tightening the timings can be worthwhile, but it's also somewhat of a science and requires rigurous stability testing. Your modules are not really what you would buy for the purpose of RAM tuning either. I mean, there is always something to gain, as the XMP especially in the secondary timings is quite conservative, but it's not a must.

If you really wanna go the whole eight years (of which a 12th gen should be capable, plus you can drop in a 13th gen CPU later), and don't want to get 2x 16 GB later, then i would just drop in another 2x 8 GB now and see if XMP still runs fine. If yes, keep it, if not, return it.

 

[CtrlAltDeluxe]

Doc_Bucket was correct in that when the game doesn't even utilize more than 16 GB (as most games wouldn't), then there is zero performance benefit from just the doubling of the RAM capacity. The performance increase from having more total RAM (not talking about the number of modules now) only comes into effect once something actually uses more RAM.

I would stay at DDR4-3600, and yes, tightening the timings can be worthwhile, but it's also somewhat of a science and requires rigurous stability testing. Your modules are not really what you would buy for the purpose of RAM tuning either. I mean, there is always something to gain, as the XMP especially in the secondary timings is quite conservative, but it's not a must.

If you really wanna go the whole eight years (of which a 12th gen should be capable, plus you can drop in a 13th gen CPU later), and don't want to get 2x 16 GB later, then i would just drop in another 2x 8 GB now and see if XMP still runs fine. If yes, keep it, if not, return it.

Thanks, some straightforward advice.

I'm leaning towards buying, just to not worry about potentially needing more in the future, considering the cpu could last for years.
The only issue is if I buy it, I keep it. We don't have a return policy in my country, not unless the product is broken. So it's definitely a risk.

Edit: I just skimmed through the QVL list for my mobo, it says:

Kingston

KF436C16RBK2/16

2x 8GB

3600

3600

SS

SK Hynix

16-20-20-39

1.35

1,2

The last section being socket support (1,2), I'm guessing it doesn't officially support 4 dimms, but could work?
The basically same kit, but 3200 and tighter timings has 1,2,4 socket support:

Kingston

KF432C16RBK2/16

2x 8GB

3200

3200

SS

SK Hynix

16-18-18-36

1.35

1,2,4

 

[citay]

The last section being socket support (1,2), I'm guessing it doesn't officially support 4 dimms, but could work?

It's a total guess, it could also mean that they only had one kit (of two modules) available. If it's a two-module kit, then they don't necessarily test with two of those kits combined. So the missing checkmark at four modules might not mean anything in particular. The only thing where it definitely means something is if they test a four-module kit and it can't do four-module operation!

Anyway, we cannot exclude all risk, but now you know the pros and cons of everything and you can hopefully make a somewhat informed decision.

 

[Doc_Bucket]

Are you sure about not being more expensive in 4 years? When DDR4 production is dropped the remaining modules will go up in price, it happened to DDR2 and DDR3.

I'm sorry, could you explain how running 4x8 will worsen my performance? I thought any stress on the memory controller will be compensated by running dual rank, and then some. I actually thought I'd get a 5 to 10% performance upgrade. Various Youtube videos show there's either a bit more performance (in 2 games a lot more), or none at all. I didn't see any performance degradation.'

Size doesn't matter in general or just 16gb vs 32gb?

I'm not sure, but I think my cpu and mobo support quad channel. I've got a 12700k and *cough* Asus TUF GAMING H670-PRO WIFI D4. There's a QVL list and there's even 4x32 RAM on that list. It does have a daisy chain topology though.

As regards the size, 32 GB will not make your RAM work faster than 16 GB. You will certainly see free physical memory in the region of min 18 GB all the time (unless running stress tests). Those 18 GB will not do anything.


I've had a look at you MoBo's specs but ASUS does not show how OC limits change with how particular slots are occupied. MSI does that, e.g. for my Tomahawk:

• 1DPC 1R Max speed up to 5000+ MHz
• 1DPC 2R Max speed up to 4500+ MHz
• 2DPC 1R Max speed up to 4400+ MHz
• 2DPC 2R Max speed up to 4000+ MHz

That makes me believe that 2x8 GB single-rank is better than 4x8GB dual-rank, at least as far as MSI is concerned. But this is a layman's understanding and in reality it may depend as citay says and I'd like to kindly refer you to his more precise explanations.

 

[Doc_Bucket]

It's possible, but i wouldn't bet on it. Historically, RAM of previous generations doesn't nosedive in price. For example, 2x 8GB of decent DDR3 are still about as expensive as 2x 8GB of DDR4 now. Price for RAM is constantly falling at the moment, but that is just the hog/pork cycle, https://en.wikipedia.org/wiki/Pork_cycle
It can also increase again.

I haven't followed the markets for many years, that's right, so in general, you must be right, especially about the Hog/Pork cycle.

I do not know what markets aladin has access to, but there's ALWAYS a moment (a day or two, if nothing better) here and there when something can be got at half price. I would vote for 2X16 GB bought at the best moment if there's no pressing need right now. It only asks for watching.

 

[CtrlAltDeluxe]

I'd like to thank you both for your input.

In the end I've decided to put my RAM on sale, and I've ordered the same kit, just 2x16, dual rank, RGB.
Or to be precise model number KF436C16RB1AK2/32

I figured I'd rather avoid any issues with having 4 DIMMs, and I've read it is an issue for some people.
Might as well go RGB, since I've got a lot of RGB going on anyway.
I was debating whether I should go for a Trident Neo B-die kit, but it's almost double the price, encroaching on DDR5 territory, which just doesn't make any sense.

Down the line I might buy a Corsair RGB dummy kit for the esthetics.