DDR5 Quad Channel with 2 DIMMs?

[iPossum]

I completed my build a couple weeks ago. I have an i7-12700K riding on an MSI MPG Z690 Edge Wifi motherboard. I haven't had any issues with the RAM and have been so focused on tuning the CPU that, until today, I hadn't even noticed that my 2 - 16GB sticks of RAM are showing up as quad-channel. At first, I thought something was wrong, so I did some research. DDR5 splits the stick into 2 separate channels, so apparently, running 2 DIMMs is technically a quad-channel configuration. My question is, what happens when you run 4 DIMMs of DDR5? Is it some kind of quasi quad/octo channel hybrid? Would it still just show up as quad-channel? Hoping someone that knows or has 4 DDR5 DIMMs in their build can help shed some light on the issue.

Thanks

 

[ir_cow]

Because DDR5 is 2x32 bit-bus it shows up as quad in CPU-Z. Intel still considers this dual channel though. I believe its because it is still considered a single channel with dual 32 bus. DDR4 was a single 64bit bus.

Let me throw in a second kit and see what CPU-Z says. I have a feeling it will still say quad.

Edit: Yep. Still says Quad. Also I knew 4x DIMM support was bad, but I top out at 5400 with these 6400 kits. Maybe if I played around with the voltages long enough 5600 could boot. It makes more sense why dual-rank kits stop at 5200. This makes me want to test what 5200 CL26 would be like. Know these can do it on their own.

 

[iPossum]

Because DDR5 is 2x32 bit-bus it shows up as quad in CPU-Z. I think Intel still considers this dual channel. Let me throw in a second kit and see what CPU-Z says. I have a feeling it will still say quad.

My man! Thank you. I'm so curious about this right now, not enough to go drop $350 on another kit. I mean, someday, but not today. I was so confused at first, and google wasnt turning up much based on what I was searching. I eventually found an article that explains how the DDR5 bus is split. That's pretty awesome for ITX boards that only have 2 DIMM slots though.

 

[looniam]

mayber ian sums it up well:

Intel 12th Gen Core Alder Lake for Desktops: Top SKUs Only, Coming November 4th

www.anandtech.com

There is no easy solution here. 2DPC (two modules per channel) doesn’t really mean much if technically channel there infers 64-bit but you’re running on a 2x32-bit channel system. Some users are calling a DDR5 module a ’channel’ with two 32-bit ‘sub-channels’, although that is more a twisting of reality, given that sub-channels are often something else in memory design. Because we’ve used the word ‘module’ to imply a 64-bit channel for so long, and because memory can be installed with more than one module per 64-bit channel, it’s actually a mess in English to find not only the correct words but also ones simple enough to not make the situation overly complex. Perhaps it’s time for some new words.

but fwiw, adding four more sticks (ddr2-4) to quad still keeps it quad, no?
so 2 more ddr5 sticks (4 modules) would still be "quad"?

 

[Wirko]

That's pretty awesome for ITX boards that only have 2 DIMM slots though.

Actually not. No matter how you count channels and what DDR version you have, you use up all channels with only two sticks. If you have four sticks, only two of them can transfer data at any given time. This applies to consumer CPUs from Intel and AMD of course, workstation and server processors have more channels.

However, in a system with only one DDR5 stick, you get two 32-bit channels, while in previous generations it's one 64-bit channel.

Well, now that we have both Intel and AMD DDR5 platforms available, we can compare how they count those channels. For Intel and 600 series motherboard makers, it's two. For AMD Rembrandt, it's four. But there is not any difference, both mean that the memory bus is 128 bits wide (not including ECC bits).

 

[ir_cow]

However, in a system with only one DDR5 stick, you get two 32-bit channels, while in previous generations it's one 64-bit channel.

Define channel.

Please correct me if I'm wrong. I was reading a Micron white paper before DDR5 went retail. From what I gathered its not that simple to compare DDR4 to DDR5. DDR5 has each bus independently send data, but they can't acess the same banks at once among other things

Check out this link for a deeper dive

DDR5 vs DDR4 DRAM - All the Advantages & Design Challenges

On July 14th, 2021, JEDEC announced the publication of the JESD79-5 DDR5 SDRAM standard signaling the industry transition to DDR5 server and client

www.rambus.com

 

[Wirko]

Define channel.

The industry seems unable to do that in an unambiguous way so don't expect too much from me. I just state the channel width when there's a possibility of confusion.

Please correct me if I'm wrong. I was reading a Micron white paper before DDR5 went retail. From what I gathered its not that simple to compare DDR4 to DDR5. DDR5 has each bus independently send data, but they can't acess the same banks at once among other things

Check out this link for a deeper dive

DDR5 vs DDR4 DRAM - All the Advantages & Design Challenges

On July 14th, 2021, JEDEC announced the publication of the JESD79-5 DDR5 SDRAM standard signaling the industry transition to DDR5 server and client

www.rambus.com

Did you ever get an impression that DDR5 is some kind of dual-port memory? That can't be true. The diagram on the page you linked and the diagram found in Micron's whitepaper make that clear. Side A stores half of the data and side B stores the other half, and what is written through A can't be read through B.

... so it's not just that the buses can't access the same banks at once; they can't ever access the same banks.

There's another issue regarding the known implementations. A and B can operate independently, but they don't have to. It depends on how complex and capable the IMC is. Here, AMD's approach may differ from Intel's, and there may be a technical reason why ADL has a total of "two" 64-bit channels while Rembrandt has "four" 32-bit channels. "Four" would suggest that A and B (and A and B on the other DIMM) are independent; the IMC keeps a separate queue of memory read/write requests for each.

 

[ir_cow]

Ohh I forgot about left and right. Like I said its been a while.

One thing I see is that the diagram is showing rank(s) for each bus. A rank is seen as a single pool of memory. Dual-Rank is two pools. Which would mean that "dual-rank" DDR5 would be like 4 pools and per dimm. 8 for 2 DIMM and 16 for 4x. Im amazed that 4x single rank DDR5-5200 even works lol. Also this may be why no 4x dual rank (4x32) 128GB exist for sale.

 

[Braegnok]

DDR5 is indeed complicated.

I started testing Dual Rank 32GB modules, they are 128-bits wide vs Single Rank modules being 64-bits wide.

The Module Information specs show Module Device Width: X4, Primary Bus Width: X32.





There is not much advantage running Dual Rank, as the memory controller can only access one rank at a time. Not exactly.

One memory bank can be accessed by the CPU, while the other can undergo a refresh cycle (readying itself to be accessed).

This process, called Rank Interleaving, is similar to SDRAM Bank Interleaving.

The masking and pipelining of refresh cycles usually results in better performance for CPU-intensive applications, as it reduces memory response times.

Personally comparing DDR5 Single and Dual Rank RAM at identical speeds does indeed show a slight advantage ranging between 3% to 5% for Dual Rank modules.

Igor's Lab also ended up with similar results testing gaming performance: https://www.igorslab.de/en/performa...in-theory-and-practice-with-cyberpunk-2077/2/

 

[iPossum]

Actually not. No matter how you count channels and what DDR version you have, you use up all channels with only two sticks. If you have four sticks, only two of them can transfer data at any given time. This applies to consumer CPUs from Intel and AMD of course, workstation and server processors have more channels.

However, in a system with only one DDR5 stick, you get two 32-bit channels, while in previous generations it's one 64-bit channel.

Well, now that we have both Intel and AMD DDR5 platforms available, we can compare how they count those channels. For Intel and 600 series motherboard makers, it's two. For AMD Rembrandt, it's four. But there is not any difference, both mean that the memory bus is 128 bits wide (not including ECC b

Because DDR5 is 2x32 bit-bus it shows up as quad in CPU-Z. Intel still considers this dual channel though. I believe its because it is still considered a single channel with dual 32 bus. DDR4 was a single 64bit bus.

Let me throw in a second kit and see what CPU-Z says. I have a feeling it will still say quad.

Edit: Yep. Still says Quad. Also I knew 4x DIMM support was bad, but I top out at 5400 with these 6400 kits. Maybe if I played around with the voltages long enough 5600 could boot. It makes more sense why dual-rank kits stop at 5200. This makes me want to test what 5200 CL26 would be like. Know these can do it on their own.
View attachment 239984

So its kinda just like switching to Geico... More.

 

[ir_cow]

DDR5 is indeed complicated.

I started testing Dual Rank 32GB modules, they are 128-bits wide vs Single Rank modules being 64-bits wide.

128-bit?? I need to go back and read the JEDEC DDR5 papers again. I've been so focused on single rank and getting the CAS down, I haven't paid much attention to dual-rank. Also I don't have any yet :/

So far the best I can do is 5200 CL26 and 6000 CL30. I'm afraid to go above 1.435v. I don't have endless supply of memory like DDR4.

 

[Ruru]

128-bit?? I need to go back and read the JEDEC DDR5 papers again. I've been so focused on single rank and getting the CAS down, I haven't paid much attention to dual-rank. Also I don't have any yet :/

So far the best I can do is 5200 CL26 and 6000 CL30. I'm afraid to go above 1.435v. I don't have endless supply of memory like DDR4.

I'd love to have spare DDR4s myself, though I have DDR2 more than for a lifetime.

 

[aliceif]

Using four sticks of DDR5 RAM will utterly demolish your frequency, there's been a bunch of content and discussion about that out there lately. You need to just look at what motherboards claim to support.
Example: MSI MPG Z690 Carbon WiFi

Max. overclocking frequency:

• 1DPC 1R Max speed up to 6666+ MHz
• 1DPC 2R Max speed up to 5600+ MHz
• 2DPC 1R Max speed up to 4000+ MHz
• 2DPC 2R Max speed up to 4000+ MHz

 

[Wirko]

DDR5 is indeed complicated.

I started testing Dual Rank 32GB modules, they are 128-bits wide vs Single Rank modules being 64-bits wide.

The Module Information specs show Module Device Width: X4, Primary Bus Width: X32.

128 bits meaning ... the total bus width of ALL ranks on a single module?

There is not much advantage running Dual Rank, as the memory controller can only access one rank at a time. Not exactly.

One memory bank can be accessed by the CPU, while the other can undergo a refresh cycle (readying itself to be accessed).

This process, called Rank Interleaving, is similar to SDRAM Bank Interleaving.

The masking and pipelining of refresh cycles usually results in better performance for CPU-intensive applications, as it reduces memory response times.

Personally comparing DDR5 Single and Dual Rank RAM at identical speeds does indeed show a slight advantage ranging between 3% to 5% for Dual Rank modules.

Igor's Lab also ended up with similar results testing gaming performance: https://www.igorslab.de/en/performa...in-theory-and-practice-with-cyberpunk-2077/2/

Yes, but it's not only the refresh that makes the difference. With more ranks, the memory controller has a bit more fine-grained control over what the DRAM chips are doing. It sends commands to and keeps the timings (tCL etc.) for each rank separately. Any given rank spends a lot (most?) of its time preparing to read or write data, and other ranks don't need to wait for that. This should improve performance a little bit when there's a lot of random access.

 

[iPossum]

Using four sticks of DDR5 RAM will utterly demolish your frequency, there's been a bunch of content and discussion about that out there lately. You need to just look at what motherboards claim to support.
Example: MSI MPG Z690 Carbon WiFi

Talking about frequency being demolished at 4000MHz is, in a way, kind of hilarious though, right? I mean, I don’t know exactly what the real world performance difference would be between, say 32GB at 5200MHz or 64GB at 4000MHz.

 

[Braegnok]

@Wirko

Hello, 128 bits meaning,... Memory Bandwidth.

Your correct, using full 4-Ranks (256-bits of memory bandwidth) is indeed optimal because of the memory cycles, (single rank) use 8 chips on one side with 64-bits of memory bandwidth. Using 2 sticks of Single Ranked RAM sticks will use 128-bits of memory bandwidth. The "Sweet Spot" is 4 ranks of memory. This can be had with 2 sticks of Dual-Ranked RAM (meaning there are chips on both sides of the PCB). That will be a total of 4-Ranks (256-bits).

WikipediA explains DDR5 Command Encoding better than I can, lol





I was using the BIOS 2X32GB SK Hynix memory preset profiles, for testing the DR modules.

The 6000MHz 2X32GB preset profile uses CL36 CR1 @ 1.435V. Need to unlock High Memory Voltage in BIOS to tighten timings, or run above 6000MHz with DR modules.

BIOS Preset Profiles:


The Cache & Memory Benchmark @ 6000MHz CL36:


If you need 64GB of DDR5 system memory,.. personally I would go with 2x32GB configuration vs 4x16GB.

The DR modules run vary hot with voltages above 1.3v, active cooling is needed for 6000MHz + profiles or anything above 1.5v to help keep modules below 50c under heavy load usage.

 

[iPossum]

I was using the BIOS 2X32GB SK Hynix memory preset profiles, for testing the DR modules.

The 6000MHz 2X32GB preset profile uses CL36 CR1 @ 1.435V. Need to unlock High Memory Voltage in BIOS to tighten timings, or run above 6000MHz with DR modules.

BIOS Preset Profiles:
View attachment 240116

The Cache & Memory Benchmark @ 6000MHz CL36:
View attachment 240117

If you need 64GB of DDR5 system memory,.. personally I would go with 2x32GB configuration vs 4x16GB.

The DR modules run vary hot with voltages above 1.3v, active cooling is needed for 6000MHz + profiles or anything above 1.5v to help keep modules below 50c under heavy load usage.

Right on. I don’t think I’ve used all 32GBs yet so, I’m in no hurry for 64 lol. RAM over clocking is my next research project. I’m still working on learning everything I can about and getting my alder lake finely tuned. I’m a little nervous about the ram though. I’ve at least overclocked cpus in the past so I had some sort of foundation. I was playing with 1 the 1 click ram profiles in MSI bios, they got me up to 5600 with no issues. Soon as I went up to 5800 no boot, red cpu debug light lmao. I just don’t know anything about tuning the rest of the ram specs yet. But hey, I’ve got time.

 

[chrcoluk]

Using four sticks of DDR5 RAM will utterly demolish your frequency, there's been a bunch of content and discussion about that out there lately. You need to just look at what motherboards claim to support.
Example: MSI MPG Z690 Carbon WiFi

A problem the industry needs to get rid off, instead its actually got worse. .

That HUB video linked on here recently, they couldnt even get a reliable post with two sticks on DDR5.

Tech isnt ready and DDR4 isnt a prime bottleneck either, so not sure why it was pushed other than for $$$.

 

[iPossum]

A problem the industry needs to get rid off, instead its actually got worse. .

That HUB video linked on here recently, they couldnt even get a reliable post with two sticks on DDR5.

Tech isnt ready and DDR4 isnt a prime bottleneck either, so not sure why it was pushed other than for $$$.

Not to mention you’ve got intel pushing motherboard manufacturers to drop DDR4 support for 700 series boards entirely. That’s absurd. I mean, it would force everyone to get DDR5 correct really quick, but that is definitely not the right answer. I think it still has the issues it does because it doesn’t have to be better right now. DDR4 isn’t a prime bottleneck like you said. Still, I went with a DDR5 board for my recent build because I don’t plan on building a new PC for me for a hot minute and wanted it as future resistant as possible. I haven’t had any issues with DDR5 personally, other than 1 no post after a bad OC. Other than that, I haven’t had any catastrophic problems. I also haven’t dived into yet so… some could pop up

 

[ir_cow]

That HUB video linked on here recently, they couldnt even get a reliable post with two sticks on DDR5.

Once you dial in the SA, IMC and TX voltages, DDR5 isn't so bad. Either the motherboard is really good at training, or absolutely sucks I've found and just won't post. BIOS updates are helping a lot. I can't get DDR5-6800 stable yet. It gets into windows but is unstable... I haven't had the time to play around with it more on different motherboards.

 

[iPossum]

Once you dial in the SA, IMC and TX voltages, DDR5 isn't so bad. Either the motherboard is really good at training, or absolutely sucks I've found and just won't post. BIOS updates are helping a lot. I can't get DDR5-6800 stable yet. It gets into windows but is unstable... I haven't had the time to play around with it more on different motherboards.

DDR5 is indeed complicated.

I started testing Dual Rank 32GB modules, they are 128-bits wide vs Single Rank modules being 64-bits wide.

The Module Information specs show Module Device Width: X4, Primary Bus Width: X32.

View attachment 240067

View attachment 240068

There is not much advantage running Dual Rank, as the memory controller can only access one rank at a time. Not exactly.

One memory bank can be accessed by the CPU, while the other can undergo a refresh cycle (readying itself to be accessed).

This process, called Rank Interleaving, is similar to SDRAM Bank Interleaving.

The masking and pipelining of refresh cycles usually results in better performance for CPU-intensive applications, as it reduces memory response times.

Personally comparing DDR5 Single and Dual Rank RAM at identical speeds does indeed show a slight advantage ranging between 3% to 5% for Dual Rank modules.

Igor's Lab also ended up with similar results testing gaming performance: https://www.igorslab.de/en/performa...in-theory-and-practice-with-cyberpunk-2077/2/

Hey, do you have any idea why my ram base clock refuse to run at 1.00? It seems like my CPU and ring also run at just slight under 1.00. In BIOS they both showed AUTO - 1.00, so I changed them off of auto and manually set them at 1.00 and still the show like this?

 

[Braegnok]

MSI had an issue years ago that with beta BIOS, when disabling spread spectrum the bus speed would not increase from 99.8MHz to 100MHz, the issue was solved later with a BIOS update.

However for a quick fix you can manually change your base clock (MHz) to 100.2,.. and see if that solves issue.

 

[iPossum]

MSI had an issue years ago that with beta BIOS, when disabling spread spectrum the bus speed would not increase from 99.8MHz to 100MHz, the issue was solved later with a BIOS update.

However for a quick fix you can manually change your base clock (MHz) to 100.2,.. and see if that solves issue.

That was actually my next step lol. Just got distracted by Elden Ring. First thing tomorrow.

 

[chugzillafx]

ok i have the acer predator po5-640-ub11... it came with hynix and i added crucial so i have all 4 slots being used so i have 48 gig i have it 16-8-16-8 so crucial-hynix-crucial-hynix look at the pictures of what my cpu-z says...now i read every comment before posting and i also experimented with just the 2x16 crucial in my system not only did it run hotter but slower...with all 4 dimms even tho there off slightly its faster and cooler...i also called crucial and they said its so close its fine not much of a difference...what are your thoughts ?

Hynix 8GB DDR5-4800 PC5-38400 Non-ECC Unbuffered CL40 288-Pin DIMM 1.1V Single Rank X16 4800 40-40-40 Memory

Crucial DDR5-4800 PC speed - PC5-38400 Density - 16GB Module type - UDIMM DIMM type - Unbuffered CAS latency - 40 Extended timings - 40-39-39 Voltage - 1.1V

 

[ir_cow]

@chugzillafx mixing 32GB with 16GB? I haven't tried this yet, but I did review a 16GB kit. It was about the same as 4800 32GB kit perf wise.