If i have 3x8gb = 24gb on a dual channel mobo, is it still dual channel?

[Space Lynx]

or will it default read to single channel?

Z390 mobo
9700k cpu.

was thinking of adding a third ram stick because i do sometimes go over 14gb of ram. but I don't want to risk losing dual channel speeds.

 

[Wavetrex]

Intel uses a hybrid approach to this.

With your 3 modules of 8GB of ram:
- First 16 GB of your memory will get dual channel speed
- Last 8 GB of it will get single channel speed.

Windows perfectly capable to handling this, as it existed for quite a while (Since the age of Core2 actually).

Quite ingenious, and if your memory utilization stays below the threshold, you'll see the same performance as with just pure dual channel.
p.s. - The unused memory is actually used as disk cache, but for that the single-channel speeds are WAY more than enough.

The same is valid for Quad-Channel systems - It uses as much as it can in the largest bandwidth possible, then dropping speed for the rest of the memory.
It is quite possible to make a crazy system on X299 with 32+16+8+4 ( 60 ) and still get full quad-channel bandwith on the first 16 GB, then triple-channel on the other 12, then dual-channel on 16 more and finally single channel on final 16 GB

~~~
I do not know how Ryzen handles this, the last AMD that I used was an Athlon 64 and that one was reverting to Single channel in this case.
But I guess the new Ryzens are smarter and doing a similar approach as modern Intels...

 

[eidairaman1]

Intel uses a hybrid approach to this.

With your 3 modules of 8GB of ram:
- First 16 GB of your memory will get dual channel speed
- Last 8 GB of it will get single channel speed.

Windows perfectly capable to handling this, as it existed for quite a while (Since the age of Core2 actually).

Quite ingenious, and if your memory utilization stays below the threshold, you'll see the same performance as with just pure dual channel.

p.s. - The unused memory is actually used as disk cache, but for that the single-channel speeds are WAY more than enough.

So its 1.5 really

 

[EarthDog]

The unused memory is actually used as disk cache, but for that the single-channel speeds are WAY more than enough.

??

Link please.. never heard of this and would like to read about it...

 

[Wavetrex]

So its 1.5 really

Not really. It's 2 AND 1
It depends on your workload size... if you run something that fully utilizes memory to the last megabyte, it will be more around "1.67", as 2/3 of the memory get full speed and 1/3 gets half speed.

But if your workload is less, then the single channel part of the memory will have less impact.
So, it can be anything between 1.67 and 2.0 "channels"

 

[eidairaman1]

Not really. It's 2 AND 1
It depends on your workload size... if you run something that fully utilizes memory to the last megabyte, it will be more around "1.67", as 2/3 of the memory get full speed and 1/3 gets half speed.

But if your workload is less, then the single channel part of the memory will have less impact.
So, it can be anything between 1.67 and 2.0 "channels"

Gtx 970 comes to mind with that last 512MB of what is really a 3.5 card.

 

[Wavetrex]

??

Link please.. never heard of this and would like to read about it...

Just open your task manger on the Memory tab.

I happen to have so much RAM that currently the system is not using all of it, but if I increase the workload and/or start moving data around, the cache size increases.

P.S. I'm in a similar situation as OP, but as quad-channel and dual-channel.

2x16 + 2x8, so a "3.33" channels config.

Gtx 970 comes to mind with that last 512MB of what is really a 3.5 card.

Not exactly.
In that situation the last controller had to switch between the 7-channel wired memory as part of 3.5 and the 1-channel last 0.5
970 only had 7 functional controllers, last one shared.

It's completely different than here, when Intel CPU still has all 2 or 4 controllers intact, but is only using one when accessing portions of memory that are not matched.

 

[dorsetknob]

Quad-channel DDR4 has replaced DDR3 on the Intel X99 LGA 2011 platform, and is also used in AMD's Threadripper platform.[18] DDR3 quad-channel architecture is used in the AMD G34 platform and in the Intel X79 LGA 2011 platform. AMD processors for the C32 platform and Intel processors for the LGA 1155 platform (e.g., Intel Z68) use dual-channel DDR3 memory instead.
The architecture can be used only when all four memory modules (or a multiple of four) are identical in capacity and speed, and are placed in quad-channel slots. When two memory modules are installed, the architecture will operate in a dual-channel mode; when three memory modules are installed, the architecture will operate in a triple-channel mode.


from wilki

 

[SoNic67]

Intel also have three channel DDR3 controllers in their LGA 1366 CPUs.
https://en.m.wikipedia.org/wiki/Multi-channel_memory_architecture

 

[EarthDog]

Just open your task manger on the Memory tab.
View attachment 116897

I happen to have so much RAM that currently the system is not using all of it, but if I increase the workload and/or start moving data around, the cache size increases.

It's cache, yes, but you are saying its page file/disk cache? I'm confused because, I have a static PF set and of course that cache value changes/dynamic (and well over what I set). A cursory google search yields nothing about a 'disk' cache (just cache - no disk references). Seems like its just memory that isn't being actively accessed...

Thanks.

 

[Space Lynx]

So if I just buy 4 ram sticks instead of 3, I will always be in dual channel mode no matter what?

 

[John Naylor]

1. Yes always buy ALL your RAM sticks in a single package

2. With dual channel boards that means 2 or 4 sticks.... tri channel 3/6 and quad channel 4/8

 

[dorsetknob]

Read your Motherboard manual and verify

 

[cucker tarlson]

or will it default read to single channel?

Z390 mobo
9700k cpu.

was thinking of adding a third ram stick because i do sometimes go over 14gb of ram. but I don't want to risk losing dual channel speeds.

you sure that's not some ram leak caused by software ?
I have 16gb too and I hardly remember it ever coming close to 14gb even though I'm used to running a game on one display,watching a stream on the other and having a dozen pages open at the same time.

 

[Space Lynx]

1. Yes always buy ALL your RAM sticks in a single package

2. With dual channel boards that means 2 or 4 sticks.... tri channel 3/6 and quad channel 4/8

i plan to just buy two packages of these when they come back in stock. but i assume since they are the exact same sticks, its the same thing as buying all 4 in same package?

you sure that's not some ram leak caused by software ?
I have 16gb too and I hardly remember it ever coming close to 14gb even though I'm used to running a game on one display,watching a stream on the other and having a dozen pages open at the same time.

it's not

 

[sneekypeet]

i plan to just buy two packages of these when they come back in stock. but i assume since they are the exact same sticks, its the same thing as buying all 4 in same package?

Binning is everything when trying to run 4 sticks without issues. Yes it can be done, but you should look for a 4 stick kit so that the kit is tested to work as intended.

 

[Sasqui]

tri channel 3/6

For x58 boards, 2 or 3 sticks will get you dual channel. At least the EVGA one I dove into.

 

[Wavetrex]

It's cache, yes, but you are saying its page file/disk cache?
...
Thanks.

It is disk cache. Has nothing to do with paging.
It's been like that since the age of Windows 3.1 and older.

An evolution of SMARTDRV for Dos (https://en.wikipedia.org/wiki/SmartDrive).

Without a disk cache, everything would be incredibly slow, as every little filename need to be accessed from the disk.
It is the main reason why computers with insufficient memory get so incredibly sluggish, because there's simply not enough spare memory for the disk cache, and if that's not enough, the system has to resort to paging memory in and out, compounding the problem.

The Read cache is always on, but by default the Write cache is OFF for safety (unless laptops, where it's on by default due to having battery-power)
However it can be turned on for any disk or ssd, very easily:
https://www.maketecheasier.com/disable-disk-write-caching-windows10/

 

[Steve-007UK]

I could be wrong and sorry if its been said already but useless things have changed over time then in my head dual channel ram has always defaulted back to single channel if you have 3 sticks on a duel channel motherboard.

What i think has been missed out and might be where some people are confusing things is when intel came up with flex memory setting in bios, basically you could mix a 2 gig and 4 gig stick of ram and it would run in dual channel flex mode.

Again i could be wrong its been time since looked things up lol maybe flex mode was having say 2x2gig and then a single stick and it still runs dual channel mode.

 

[Wavetrex]

1. Yes always buy ALL your RAM sticks in a single package

2. With dual channel boards that means 2 or 4 sticks.... tri channel 3/6 and quad channel 4/8

False. (Today).
There's absolutely no need to buy anything in multiple sticks.

In the past (DDR1, DDR2) manufacturers were not respecting standards exactly, and there was a chance of the two different brands interfering with each other. (And also not all modules have the SPD chip in them, so the BIOS had no clue whatsoever what memory chips are installed)

Today however that is long past history, DDR3 and DDR4 follow JEDEC standards very strictly.

When everything is on "Auto" in BIOS, the system will simply boot with the slowest settings from SPD, the bios is reading settings as it's enumerating chips, and the picking the numbers that apply to all, and boot with that.
When setting manually, obviously all modules on the same channel group must be able to run them, otherwise booting will fail.

I could be wrong and sorry if its been said already but useless things have changed over time then in my head dual channel ram has always defaulted back to single channel if you have 3 sticks on a duel channel motherboard.

I've already said that Intel CPU's are using a Hybrid approach.

Long read, warning:
https://software.intel.com/en-us/articles/how-memory-is-accessed

It's called FLEX MODE, not Hybrid mode. My mistake in previous posts.
https://www.intel.com/content/www/us/en/support/articles/000005657/boards-and-kits.html#flex

 

[EarthDog]

So if I just buy 4 ram sticks instead of 3, I will always be in dual channel mode no matter what?

On a dual channel platform, yes.

Today however that is long past history, DDR3 and DDR4 follow JEDEC standards very strictly.

The concern is with stability... users should ALWAYS strive to purchase matching sticks!!!

 

[Wavetrex]

Some screenshots:

Observe the Quad channels, with this odd memory quantity; Also the different manufacturers, slightly different timings as well.

The system simply picked "36" for tRAS which works with both (It's also using 69 for tRC, even if the Corsair modules support faster 52)

What do you know, Corsair and Kingston can be friends ;-)

 

[agent_x007]

Just install two Single Sided sticks in channel "A" and one Dual Sided stick on channel "B".
That way you will get "standard" Dual Channel (no flexmode).
Of course if you already two dual sided modules, you are screwed :/

Also, if memory can work on current UEFI/BIOS setttings - it doesn't matter who made it it should work in Dual/Triple/Quad/Hex Channel (assuming IMC is any good).

EDIT : Forgot to add : Each single sided module must have half of the capacity of the Dual Sided one

 

[EarthDog]

Just install two Single Sided sticks in channel "A" and one Dual Sided stick on channel "B".

I don't think it works that way... dual-sided shouldn't have anything to do with channels...

 

[Space Lynx]

Just install two Single Sided sticks in channel "A" and one Dual Sided stick on channel "B".
That way you will get "standard" Dual Channel (no flexmode).
Of course if you already two dual sided modules, you are screwed :/

Also, if memory can work on current UEFI/BIOS setttings - it doesn't matter who made it it should work in Dual/Triple/Quad/Hex Channel (assuming IMC is any good).

i will just buy a 4 stick kit together to be safe. thanks everyone and take care