# Why is Quad-channel not supported by AM4 (or by LGA1151)?



## m&m's (Feb 13, 2018)

After seeing reviews of Ryzen APUs (which are limited by memory bandwith (IGP wise)), I asked myself why isn't quad-channel standard? Only X399 and LGA2011 supports it.
Quad-channel supports triple and dual-channel so wouldn't everybody benefits from it?
With current memory prices, people could buy 4 sticks of 2400MHz instead of 2 of 3200MHz and save some money.
Even at 3200MHz the IGP is still bottlenecked by RAM speed so when RAM prices go down (if they do) people could get 4 sticks of 3200MHz and net some gains.
TechSpot compared dual-channel and single channel and the benefits are humongous (as expected).
Would the implementation of quad-channel be too expensive? What are your thoughts?






TechSpot link: https://www.techspot.com/review/1574-amd-ryzen-5-2400g-and-ryzen-3-2200g/page8.html


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## CrAsHnBuRnXp (Feb 13, 2018)

Quad channel is typically more expensive and is an enthusiast level technology.


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## TheoneandonlyMrK (Feb 13, 2018)

Why would someone spend so much on ram for an Apu or any lower to mainstream pc.

In general either company could have put more memory channels in but Amd see no need since they make do with two to three cpu designs per generation and use such things to differentiate between spec and price, Intel make more designs but use far more cutting techniques to differentiate even further hence their massive Sku list.

Would be nice but it's impractical at low to mid range due to pricing imho.


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## Gasaraki (Feb 13, 2018)

Umm, doesn't work that way.

1. They don't build chipsets for the benefit of mankind.
2. Quad-Channel 2400 is not faster than Dual-Channel 3200.
3. Your chart is comparing single vs. dual channel. It doesn't scale to quad-channel. When you have a single lane road and you make it double lane, you can get to your destination faster. Making the road four lanes is not going to make it much faster than 2 lanes. (unless you have A LOT of cars ie. data going through)


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## peche (Feb 13, 2018)

Gasaraki said:


> 1. They don't build chipsets for the benefit of mankind.


sounds so intel, indeed,


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## repman244 (Feb 13, 2018)

theoneandonlymrk said:


> Why would someone spend so much on ram for an Apu or any lower to mainstream pc.
> 
> In general either company could have put more memory channels in but Amd see no need since they make do with two to three cpu designs per generation and use such things to differentiate between spec and price, Intel make more designs but use far more cutting techniques to differentiate even further hence their massive Sku list.
> 
> Would be nice but it's impractical at low to mid range due to pricing imho.



Yet in the past we saw big improvements of IGP performance with faster/overclocked RAM so there actually is some performance to gain. If it would actually benefit from quad channel we cannot prove for now.


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## windwhirl (Feb 13, 2018)

Don't you need at least 4 memory sticks for quad channel? Consider that not everyone fills their motherboards to the brim regarding RAM. Only enthusiasts install 32 or 64 GB of RAM (is there any sense in installing 4x4GB of RAM? Honest question here, since I don't really know...), and only if they can pay for it without sacrificing anything else (16 GB tends to be more than enough unless you go hardcore or have any app/game that needs a lot of RAM, though these days may not last for long). Heck, the only reason I went from 16 to 24 GB of RAM was that I wanted no pagefile (saving myself some space on a 240 GB SSD and avoiding any performance loss that I could have incurred in because of said pagefile). So, the market most mainstream mobos are targeted at don't really show much interest in quad channel.

Also, quad channel memory doesn't have as much of a benefit as going from single to dual channel. Even with the increased memory bandwidth, you don't really notice much of a difference, unless whatever you do is really dependent on memory bandwidth (like WinRAR or 7-Zip).


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## m&m's (Feb 13, 2018)

CrAsHnBuRnXp said:


> Quad channel is typically more expensive and is an enthusiast level technology.





theoneandonlymrk said:


> Why would someone spend so much on ram for an Apu or any lower to mainstream pc.


That's the thing, people could actually save money by buying cheaper RAM and still have decent memory bandwidth for the IGP.



theoneandonlymrk said:


> In general either company could have put more memory channels in but Amd see no need since they make do with two to three cpu designs per generation and use such things to differentiate between spec and price, Intel make more designs but use far more cutting techniques to differentiate even further hence their massive Sku list.


I understand what you're saying but I don't think quad-channel would've stolen sales from Threadripper or any higher CPU designs since most people who buy Threadripper is for it's cores and memory capacity not specifically it's memory bandwidth.



theoneandonlymrk said:


> Would be nice but it's impractical at low to mid range due to pricing imho.





CrAsHnBuRnXp said:


> Quad channel is typically more expensive and is an enthusiast level technology.


Yeah, but that's the main question in my head, how much more would it actually cost? If it means motherboards and CPUs would cost $5 more, I wouldn't care.



Gasaraki said:


> Umm, doesn't work that way.
> 
> 1. They don't build chipsets for the benefit of mankind.
> 2. Quad-Channel 2400 is not faster than Dual-Channel 3200.
> 3. Your chart is comparing single vs. dual channel. It doesn't scale to quad-channel. When you have a single lane road and you make it double lane, you can get to your destination faster. Making the road four lanes is not going to make it much faster than 2 lanes. (unless you have A LOT of cars ie. data going through)


Not faster, but offers more bandwidth and current APUs are bandwidth limited.



windwhirl said:


> Don't you need at least 4 memory sticks for quad channel? Consider that not everyone fills their motherboards to the brim regarding RAM. Only enthusiasts install 32 or 64 GB of RAM (is there any sense in installing 4x4GB of RAM? Honest question here, since I don't really know...), and only if they can pay for it without sacrificing anything else (16 GB tends to be more than enough unless you go hardcore or have any app/game that needs a lot of RAM, though these days may not last for long). Heck, the only reason I went from 16 to 24 GB of RAM was that I wanted no pagefile (saving myself some space on a 240 GB SSD and avoiding any performance loss that I could have incurred in because of said pagefile). So, the market most mainstream mobos are targeted at don't really show much interest in quad channel.
> 
> Also, quad channel memory doesn't have as much of a benefit as going from single to dual channel. Even with the increased memory bandwidth, you don't really notice much of a difference, unless whatever you do is really dependent on memory bandwidth (like WinRAR or 7-Zip).


I'm talking IGP wise not CPU wise. The benefit of quad-channel could be pretty good for the IGP.

And like I said quad-channel supports dual and triple channel so people could still only use 2 sticks if they wanted. My question should be read more in the sense of "Why not"?


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## eidairaman1 (Feb 13, 2018)

Because AM4/1150 are MSDT and TR4/2066 are HEDT


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## agent_x007 (Feb 13, 2018)

I guess Quad Channel would require around 1500-2000 pins in socket (depending on PCI-e lanes).
There are no technical limitations to do this (and limit max. DIMM slot number to 4 to keep server guys apart), however if it can be done cheaply is doubtful...
Also, HBM 2.0 can make over Dual-channel memory support iGPU pointless in the long run.
Last thing : It would "kill" HEDT platform as we know it (which at that point the only big selling point would be more PCI-e lanes/Cores).

Last thing is iGPU performance :
You simply may not have transistor budget for iGPU for 256/192-bit memory bus to be worth it.


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## eidairaman1 (Feb 13, 2018)

agent_x007 said:


> I guess Quad Channel would require around 1500-2000 pins in socket (depending on PCI-e lanes).
> There are no technical limitations to do this (and limit max. DIMM slot number to 4 to keep server guys apart), however if it can be done cheaply is doubtful...
> Also, HBM 2.0 can make over Dual-channel memory support iGPU pointless in the long run.
> Last thing : It would "kill" HEDT platform as we know it (which at that point the only big selling point would be more PCI-e lanes/Cores).
> ...



We had HEDT with MSDT during the SktA days


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## agent_x007 (Feb 13, 2018)

eidairaman1 said:


> We had HEDT with MSDT during the SktA days


True 
However, after that point both AMD and Intel discovered how to make even more money/profit.


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## erocker (Feb 13, 2018)

Products are separated into segments where they are needed for various tasks. Gaming/mainstream platforms don't need quad channel and actually in many cases benefit from not having it.


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## eidairaman1 (Feb 13, 2018)

agent_x007 said:


> True  and LGA 775 days as well.
> However, after that point both AMD and Intel discovered how to make even more money/profit.



Skt A the chips were same exact socket, with minor mod you could run 2 Athlon XPs in a DP board or a DP based cpu in a SP skt lol.

FAB51 has all that info.

Now with 775, 771 had to be reoriented, the keytabs broken and a cpu mod to make 771s work in 775


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## m&m's (Feb 13, 2018)

agent_x007 said:


> Last thing : It would "kill" HEDT platform as we know it (which at that point the only big selling point would be more PCI-e lanes/Cores).


And way more memory capacity. I mean they would still have quad-channel, they don't lose anything. Is the memory bandwidth really that much of a selling point for HEDT? I taught HEDT guys looked at capacity way before bandwidth.


erocker said:


> Products are separated into segments where they are needed for various tasks. Gaming/mainstream platforms don't need quad channel and actually in many cases benefit from not having it.


Back with the first AM3 APUs, we already knew they were bandwidth limited so while they were still working on AM4 knowing they would release new APUs that would still be bandwith limited, adding quad-channel support wouldn't have been a good solution? Unless they taught DDR4 was gonna be enough. I understand that 99% of the time quad-channel brings nothing to the mainstream user, but again I'm talking IGP wise not CPU.


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## agent_x007 (Feb 13, 2018)

m&m's said:


> And way more memory capacity. I mean they would still have quad-channel, they don't lose anything. Is the memory bandwidth really that much of a selling point for HEDT? I taught HEDT guys looked at capacity way before bandwidth.


You don't buy something you don't need. HEDT is by definition more expensive than mainstream and at this point (mainstream Quad Channel), for simple "more capacity" you simply should go Xeon, not HEDT.
Unless you really want/need Overclocking capability, and all that RGB stuff.


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## m&m's (Feb 13, 2018)

agent_x007 said:


> You don't buy something you don't need. HEDT is by definition more expensive than mainstream and at this point (mainstream Quad Channel), for simple "more capacity" you simply should go Xeon, not HEDT.
> Unless you really want/need Overclocking capability, and all that RGB stuff.


Exactly, so is quad-channel a real selling point to have (by making it not available on lower ends)?


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## newtekie1 (Feb 13, 2018)

It comes down to the memory controller being bigger, that makes the CPU die larger, and die space is  definitely something to consider in the cost of production.

Look at some of the die shots with the parts labeled, the memory controller takes up quite a bit of space, something like almost 10% of the die on a dual-channel Kabylake die.  Now, if they had to double that to make a quad-channel controller, you're talking almost 20% of the die taken up just for the memory controller.  That's too much die space for a sub-$500 processor.


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## agent_x007 (Feb 13, 2018)

eidairaman1 said:


> Now with 775, 771 had to be reoriented, the keytabs broken and a cpu mod to make 771s work in 775


Mod kits for LGA 771 are cheap as chips, and you don't have to breake tabs on MB - simply drill new holes for them on CPUs PCB (or buy CPU with pre-done holes and LGA 771 mod).
Also, you don't need all that for LGA 775 Xeons to work on LGA 775 board.

@m&m's I think, yes it is.
You have a pretty good reason to jack-up prices even more if you implement it.
Quad Channel support (for now), is not about "Why ?" - but about "How much ?".


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## eidairaman1 (Feb 13, 2018)

agent_x007 said:


> Mod kits for LGA 771 are cheap as chips, and you don't have to breake tabs on MB - simply drill new holes for them on CPUs PCB (or buy CPU with pre-done holes and LGA 771 mod).
> Also, you don't need all that for LGA 775 Xeons to work on LGA 775 board.
> 
> @m&m's I think, yes it is.
> ...



I was going by an old procedure, its socket tabs lol


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## Vya Domus (Feb 13, 2018)

Gasaraki said:


> 2. Quad-Channel 2400 is not faster than Dual-Channel 3200.



It is.


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## xorbe (Feb 13, 2018)

It would raise the cost (# of pins, motherboard size and trace routing) for everyone, and OEMs would still sell systems with one stick of RAM (or order up custom motherboards with just one channel).


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## erocker (Feb 13, 2018)

m&m's said:


> And way more memory capacity. I mean they would still have quad-channel, they don't lose anything. Is the memory bandwidth really that much of a selling point for HEDT? I taught HEDT guys looked at capacity way before bandwidth.
> 
> Back with the first AM3 APUs, we already knew they were bandwidth limited so while they were still working on AM4 knowing they would release new APUs that would still be bandwith limited, adding quad-channel support wouldn't have been a good solution? Unless they taught DDR4 was gonna be enough. I understand that 99% of the time quad-channel brings nothing to the mainstream user, but again I'm talking IGP wise not CPU.


I don't think it would be cost effective for the platform. They already have Threadripper.


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## newtekie1 (Feb 13, 2018)

xorbe said:


> It would raise the cost (# of pins, motherboard size and trace routing) for everyone, and OEMs would still sell systems with one stick of RAM (or order up custom motherboards with just one channel).



In reality, it wouldn't need any extra pins and likely very minor trace re-working on motherboards.


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## m&m's (Feb 13, 2018)

erocker said:


> I don't think it would be cost effective for the platform. They already have Threadripper.


But they don't plan on releasing APUs on Threadripper don't they? Also Threadripper CPUs are all $500+ and the motherboards are all $300+. Not really the kind of consumers AMD is trying to attract with APUs.

I just think that quad-channel would make the APUs much more interesting. RX560 perfomance could be achievable instead of RX550 (2x faster).


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## eidairaman1 (Feb 13, 2018)

m&m's said:


> But they don't plan on releasing APUs on Threadripper don't they? Also Threadripper CPUs are all $500+ and the motherboards are all $300+. Not really the kind of consumers AMD is trying to attract with APUs.
> 
> I just think that quad-channel would make the APUs much more interesting. RX560 perfomance could be achievable instead of RX550 (2x faster).



Intel don't have ig on their cpus for skt2066.


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## TheoneandonlyMrK (Feb 13, 2018)

Memory isn't cheap though and for four sticks never was , even lower speed are expensive in four stick form , your taking possible server memory.

Consider the economies of scaling it too , we're already paying high prices without everything using four channels worth.

Im surprised memory companies aren't pushing for six


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## m&m's (Feb 13, 2018)

eidairaman1 said:


> Intel don't have ig on their cpus for skt2066.


Ok??
Never said it did or needed to.



theoneandonlymrk said:


> Memory isn't cheap though and for four sticks never was , even lower speed are expensive in four stick form , your taking possible server memory.
> 
> Consider the economies of scaling it too , we're already paying high prices without everything using four channels worth.
> 
> Im surprised memory companies aren't pushing for six



Thing is, 4x4GB 2400MHz cost less than 2x8GB 3200MHz.


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## eidairaman1 (Feb 14, 2018)

m&m's said:


> Ok??
> Never said it did or needed to.
> 
> 
> ...



This is in regards to this.

"But they don't plan on releasing APUs on Threadripper don't they?"


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## TheoneandonlyMrK (Feb 14, 2018)

m&m's said:


> Ok??
> Never said it did or needed to.
> 
> 
> ...


Their are the other points I mentioned plus a processors integrated memory controller is made For task because of its relative size in what is a tight die budget , so low cost chips get less space allocated.
It's a big user of power too twice the amount, twice the heat and power draw to deal with in the Imc and system ,all thing's are relative at every price point.


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## m&m's (Feb 14, 2018)

eidairaman1 said:


> This is in regards to this.
> 
> "But they don't plan on releasing APUs on Threadripper don't they?"



I believe you misunderstand why I said the above.

I said this in response to erocker's "They already have Threadripper."

What I meant was: there is no APU on Threadripper so even if Threadripper has quad-channel, APUs don't benefit from it. Thus why I mentioned AM4 in the title.


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## newtekie1 (Feb 14, 2018)

m&m's said:


> I just think that quad-channel would make the APUs much more interesting. RX560 perfomance could be achievable instead of RX550 (2x faster).



I don't actually think it would make that much of a difference.  The fact is the iGPU doesn't have the stream processors to reach RX560 performance.  Eventually, adding more bandwidth just doesn't help that much, the law of diminishing returns kicks in.  And I bet the point where more bandwidth doesn't really help is right around the dual-channel point.  AMD is smart, they aren't going to gripple a good GPU with bandwidth, instead they designed the GPU to match the bandwidth available to it.


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## cadaveca (Feb 14, 2018)

m&m's said:


> I asked myself why isn't quad-channel standard?



You should also be asking yourself "Are these APUs benefitting from greater bandwidth, or is it lower latency?"


Then you might also want to know that quad-channel, because there are more channels to address, adds in latency compared to dual-channel.


You see there was this consumer videocard that posed that exact question... the 2900XT. It's successor, the 3870, was pretty much the same chip, but with half the memory bandwidth.


So, then you might wonder if the GPU side of the APU might benefit from its own dedicated memory? We can investigate this soon, I think.


Yet ultimately, you are asking high-performance questions of a low-power use platform.


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## RejZoR (Feb 14, 2018)

GPU memory bandwidth is a different thing though. HD3870 could halve half the bus width because they gave it so much ridiculously faster memory. Even f you have fewer lanes, you can drive Ferrari's full speed on those few lanes. Second reason why this is easier achievable on graphic cards is because memory modules they stick on graphic cards are verified functional with the memory controller at given speed. Good luck running those stupid fast 4500MHz RAM modules on, well, pretty much anything. It's why RAM thing is not that easy in regards for speed. It's a lot easier populating 4x quad channels with slower speed RAM modules than 2x dual channel with hyper fast RAM sticks.


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