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

[m&m's]

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

 

[CrAsHnBuRnXp]

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

 

[TheoneandonlyMrK]

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.

 

[Gasaraki]

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)

 

[peche]

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

sounds so intel, indeed,

 

[repman244]

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.

 

[windwhirl]

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).

 

[m&m's]

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

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.

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.

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

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.

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.

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"?

 

[eidairaman1]

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

 

[agent_x007]

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.

 

[eidairaman1]

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.

We had HEDT with MSDT during the SktA days

 

[agent_x007]

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.

 

[erocker]

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.

 

[eidairaman1]

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

 

[m&m's]

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.

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.

 

[agent_x007]

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.

 

[m&m's]

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)?

 

[newtekie1]

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.

 

[agent_x007]

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 ?".

 

[eidairaman1]

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 ?".

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

 

[Vya Domus]

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

It is.

 

[xorbe]

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).

 

[erocker]

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.

 

[newtekie1]

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.

 

[m&m's]

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).