[SOLVED] 2x8GB or 3x8GB ?

Malikboi_

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Feb 9, 2017
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Hello,
I'm running a Corsair Vengeance LPX (2x8GB) CL16 @ 3000Mhz {XMP already enabled}
I also have a 3rd RAM just lying at my desk to be used. It's literally the same RAM, the latency and capacity and everything is same.
So I want to know if there is any performance decrease in running the RAM in triple channel?
I really don't need that much RAM but if i can get more performance(even if it's a little) then why not I use it?
Please don't tell me that I don't need it or anything because I can't sell it and it's of no use currently.

Specs:
CPU-i7 9700k
GPU-RTX 2060
Motherboard-Gigabyte Z390-M
PSU- Gigabyte PB500
CPU Cooler- CM ML240 Lite Non-RGB
Cabinet- Gigabyte C200 Glass
 

PC Tailor

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I also have a 3rd RAM just lying at my desk to be used. It's literally the same RAM, the latency and capacity and everything is same.
Firstly this does not guarantee compatibility. RAM is ONLY guaranteed in the form sold. Ensuring latency/size/speed etc. is the same is just a way of trying to minimise risk, but absolutely doesn't eliminate it. Mixed modules are a gamble so you'd have to test if it works nicely to begin with.

So I want to know if there is any performance decrease in running the RAM in triple channel?
This isn't how channels work, having 3 RAM modules is not the same as Triple Channel, you need the motherboard to ALSO have that many channels (and a channel is not the same as a RAM slot).

You have a dual channel board, so you can only run single or dual channel. Adding a third RAM module will add more RAM into one of the currently used channels and can cause a performance decrease as you now have 2 modules being accessed through 1 lane of traffic.

I really don't need that much RAM but if i can get more performance(even if it's a little) then why not I use it?
Well if you don't need it, it will yield ZERO performance boost. So there really isn't any point. RAM only adds performance if you're splitting into channels and if your applications actually exceed usage of the current RAM you have.

:)
 
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PC Tailor

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I also have a 3rd RAM just lying at my desk to be used. It's literally the same RAM, the latency and capacity and everything is same.
Firstly this does not guarantee compatibility. RAM is ONLY guaranteed in the form sold. Ensuring latency/size/speed etc. is the same is just a way of trying to minimise risk, but absolutely doesn't eliminate it. Mixed modules are a gamble so you'd have to test if it works nicely to begin with.

So I want to know if there is any performance decrease in running the RAM in triple channel?
This isn't how channels work, having 3 RAM modules is not the same as Triple Channel, you need the motherboard to ALSO have that many channels (and a channel is not the same as a RAM slot).

You have a dual channel board, so you can only run single or dual channel. Adding a third RAM module will add more RAM into one of the currently used channels and can cause a performance decrease as you now have 2 modules being accessed through 1 lane of traffic.

I really don't need that much RAM but if i can get more performance(even if it's a little) then why not I use it?
Well if you don't need it, it will yield ZERO performance boost. So there really isn't any point. RAM only adds performance if you're splitting into channels and if your applications actually exceed usage of the current RAM you have.

:)
 
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TJ Hooker

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Combining RAM that wasn't purchased together as a kit can cause issues, even if they're the same model. If you can install the 3rd stick and everything is still stable at the same speed, then I don't think it should cause any performance loss.

At the same time, unless you were previously running out of RAM (unlikely), you probably won't see any performance gain either.
 

Malikboi_

Commendable
Feb 9, 2017
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Firstly this does not guarantee compatibility. RAM is ONLY guaranteed in the form sold. Ensuring latency/size/speed etc. is the same is just a way of trying to minimise risk, but absolutely doesn't eliminate it. Mixed modules are a gamble so you'd have to test if it works nicely to begin with.


This isn't how channels work, having 3 RAM modules is not the same as Triple Channel, you need the motherboard to ALSO have that many channels (and a channel is not the same as a RAM slot).

You have a dual channel board, so you can only run single or dual channel. Adding a third RAM module will add more RAM into one of the currently used channels and can cause a performance decrease as you now have 2 modules being accessed through 1 lane of traffic.


Well if you don't need it, it will yield ZERO performance boost. So there really isn't any point. RAM only adds performance if your splitting into channels and if your applications actually exceed usage of the current RAM you have.

:)

Woah. That so quick. Thank you for answering. I guess I'll try selling it :D
 
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Sep 14, 2019
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You have a dual channel board, so you can only run single or dual channel. Adding a third RAM module will add more RAM into one of the currently used channels and can cause a performance decrease as you now have 2 modules being accessed through 1 lane of traffic.
By deduction, is the same true for 4 RAM sticks instead of 3 ?

In other words, will 4x8 GB, on a dual channel board, be slower than 2x16 ?
 
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PC Tailor

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By deduction, is the same true for 4 RAM sticks instead of 3 ?

In other words, will 4x8 GB, on a dual channel board, be slower than 2x16 ?
Correct (generally) it's not that EVERY situation ends up with less performance, but usually it does (depends on how you use the RAM really)

In effect I like to see the channels as a lane of traffic the RAM is where all the cars come from, if you have dual channel, you've got 2 lanes of traffic, so all the data has both lanes to get to the destination quicker rather than queueing in 1 lane.

If you have 4 modules in dual channel, you've still only got 2 lanes of traffic, but now double the amount if cars, which can then cause Congestion.

However with a Quad Channel board, you then have 4 lanes of traffic so the congestion is eased.

Simplified but tends to put it into a clear perspective :)
 
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It will depend on the game development and how the CPU calls that data too.

Same kind of situation where dual GPUs can cause some improvement and in others it just causes problems.

Thus my response above that its not EVERY situation that it will be slower, but generally it is.

I also take some of those benchmarks wihh a big pinch of salt because you can see even just from the start) that the CPU is throttling at times, so it kind of removed the validity of what is actually causing the FPS difference.
 

PC Tailor

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Thanks you. I do take these reviews with a pinch of salt usually but in this case it’s not the only one, I have seen others since but with no good expectation why.
No you're right. It's a very valid point as we all know it's never a blanket answer with anything on computers, there are always outliers, just the power of YouTube also means we can't see how controlled the situation is and obviously there are so many variables it can be impossible to deduce everything!

But a very valid question that should be asked really, and may be worth looking into how it can differ by game etc.
 
Sep 14, 2019
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Correct (generally) it's not that EVERY situation ends up with less performance, but usually it does (depends on how you use the RAM really)

In effect I like to see the channels as a lane of traffic the RAM is where all the cars come from, if you have dual channel, you've got 2 lanes of traffic, so all the data has both lanes to get to the destination quicker rather than queueing in 1 lane.

If you have 4 modules in dual channel, you've still only got 2 lanes of traffic, but now double the amount if cars, which can then cause Congestion.

However with a Quad Channel board, you then have 4 lanes of traffic so the congestion is eased.

Simplified but tends to put it into a clear perspective :)
Thanks. That makes sense.

I'm just baffled as to why all of this kind of info is not made more readily accessible to the general PC building public. i.e. why don't mobo and RAM manufacturers print this stuff in BOLD 36 font on the front of their manuals - BUY RAM ONLY IN MATCHED KITS, AND FOR THIS MOBO, PREFER 2 STICKS OVER 4. It is almost like an unwritten rule that most people are not going to see ! Yes, I've seen it briefly mentioned in mobo manuals, but they never said "Since this is a dual channel mobo, prefer 2 sticks over 4 if possible."

Kind of like you go to Subway sandwiches, and in small unreadable font somewhere, it says something like "Meatball sub - 1 million calories ... heart attack". Who's going to see it ?!!!

I had to come to this forum and ask quite a few questions and read several posts to understand the deal ^ with RAM (and I'm a millenial software engineer ! ... what if I were a non-tech-savvy guy who was trying his hand at building PCs for the first time ? How would I ever know all this ?)

Even quite a few PC builders are people who only have a superficial understanding of computer hardware and logic. They are good at assembling parts but don't necessarily understand the most intrinsic details. For their sake at least (but really, for all builders), mobo manuals should have at least one page dedicated to "part selection".

After all, if I was manufacturing toilets, I would tell my customers "Don't eat more than 5 hamburgers in one meal ... and preferably without cheese" What goes IN my product will determine its performance :LOL:
 
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TJ Hooker

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I completely agree with everything else but there are reviews showing 4x4gb outperforming 2x8gb for gaming and I have not found a reasonable explanation why. Here is a thread I started to try and get answers to understand this and it contains comparisons for both AMD and Intel https://forums.tomshardware.com/threads/2x8gb-vs-4x4gb-gaming-comparison-intel.3479216/
It's probably a result of having four memory ranks in total rather than two. Going to two ranks per memory channel improves performance due to rank interleaving. This can either be achieved by two dual rank DIMMs or 4 single rank DIMMs.

Recent 8GB DIMMs are typically going to be single rank, which means that if you're buying a new kit you may have to get 32GB (4x8 or 2x16) to get a total of four ranks.

More info here: https://www.tomshardware.com/reviews/amd-ryzen-3000-best-memory-timings,6310.html
 
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It's probably a result of having four memory ranks in total rather than two. Going to two ranks per memory channel improves performance due to rank interleaving. This can either be achieved by two dual rank DIMMs or 4 single rank DIMMs.

Recent 8GB DIMMs are typically going to be single rank, which means that if you're buying a new kit you'd probably have to get 32GB (4x8 or 2x16) to get a total of four ranks.

More info here: https://www.tomshardware.com/reviews/amd-ryzen-3000-best-memory-timings,6310.html
Thank you, best answer yet. Appreciated
 

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