Doubt with motherboard RAM compatibilities and Processor

becontroller · Oct 10, 2017

Hello,i have a doubt,why several motherboards have dual memory channel arquitecture and they admit x4 DIMM channels when intel LGA 1151 series dont allow more than 2 memory channels?
It just doesnt make sense.I dont understand that part of compatibility.Im so confused now.Can someone explain me this in detail?

I provide a link from one of the motherboards and processor that shows this specifications.

MB: https://www.pcfactory.cl/producto/24675-m-b-intel-h270-pc-mate

Processor: https://www.pcfactory.cl/producto/24815-cpu-core-i5-7600k-3-8ghz-6mb-1151-

Websites are in spanish so please make use of google translator or other feature to get into english.

Thank you.

raisonjohn · Oct 10, 2017

If a motherboard has dual-memory channel architecture and it has 4x DIMM slots, then, this means you can plug in 2 RAM sticks PER channel. You can run dual-memory speeds using just 2 out of the 4 slots (the ones usually having the same colored slots), where in this case, you are running only 1 RAM stick PER channel. Using all 4 out of the 4 slots puts more stress in the memory controller.

When a motherboard has dual-memory channel architecture and it only has 2x DIMM slots, then, this means you can only plug in 1 RAM stick PER channel.

The LGA1151 platform uses dual-channel memory architecture, such as the Msi H270 PC Mate motherboard and the corresponding Intel CPU you selected.

Motherboards having quad-channel memory architecture are usually (not always) have 8x DIMM slots. This means you can run quad-channel speeds using either 4x RAM sticks (i.e., 1 stick PER channel) or populating all slots with 8x RAM sticks (i.e., using 2 sticks PER channel). There are some motherboard models that only have 4x RAM slots but still run in quad-channel memory architecture.

Currently, the LGA2066 platform uses quad-channel memory architecture. Previously, the LGA2011-v3 platform is another example. These platforms use different Intel CPUs than the one you linked.

becontroller · Oct 11, 2017

raisonjohn :

If a motherboard has dual-memory channel architecture and it has 4x DIMM slots, then, this means you can plug in 2 RAM sticks PER channel. You can run dual-memory speeds using just 2 out of the 4 slots (the ones usually having the same colored slots), where in this case, you are running only 1 RAM stick PER channel. Using all 4 out of the 4 slots puts more stress in the memory controller.

When a motherboard has dual-memory channel architecture and it only has 2x DIMM slots, then, this means you can only plug in 1 RAM stick PER channel.

The LGA1151 platform uses dual-channel memory architecture, such as the Msi H270 PC Mate motherboard and the corresponding Intel CPU you selected.

Motherboards having quad-channel memory architecture are usually (not always) have 8x DIMM slots. This means you can run quad-channel speeds using either 4x RAM sticks (i.e., 1 stick PER channel) or populating all slots with 8x RAM sticks (i.e., using 2 sticks PER channel). There are some motherboard models that only have 4x RAM slots but still run in quad-channel memory architecture.

Currently, the LGA2066 platform uses quad-channel memory architecture. Previously, the LGA2011-v3 platform is another example. These platforms use different Intel CPUs than the one you linked.

Thanks for the reply,i still didnt understand.Lets say if i put all my rams sticks x4 they will still not work because of the processor.

BFG-9000 · Oct 11, 2017

Those pages don't claim 4 channels anywhere--they say 4 slots. 2 slots per channel has been common and even standard since DDR1 arrived 17 years ago in 2000. Before that with SDRAM, 4 slots per channel was allowed at low bus speeds, dropping to three at higher speeds due to reflection issues with termination. And then famously in 1999 RAMBUS had to drop their spec from 3 slots to 2 per channel after boards were designed due to a signal integrity problem--the 3rd slot was then reserved for a terminator card.

raisonjohn · Oct 11, 2017

becontroller :

You're welcome. But, what do you mean it will not work?? Your processor, the Intel Core i5-7600K, has a maximum dual channel memory:

"Memory Specifications
Max # of Memory Channels - 2"
Source: https://ark.intel.com/products/97144/Intel-Core-i5-7600K-Processor-6M-Cache-up-to-4_20-GHz

Your motherboard, the Msi H270 PC Mate, has a dual channel memory architecture:

"MEMORY CHANNEL - Dual"
Source: https://www.msi.com/Motherboard/H270-PC-MATE/Specification

As said in my previous reply, if a motherboard has 4x SLOTS - it does NOT necessarily mean it has 4 channels. A slot is not synonymous to a channel. In your motherboard's case, it has 4x SLOTS (not channels), but only works in 2x CHANNELS.

To achieve dual channel speeds, you need to plug the 2x RAM sticks on the slots assigned to a specific channel. Typically, Channel A is comprised of Slot 1 and Slot 2; then, Channel B is comprised of Slot 3 and Slot 4.

Using that Msi H270 PC Mate, if you plug:
1 stick (any slot) = Single Channel Speed with 1 stick in 1 channel
2 sticks (in slots 1 and 2) = Single Channel Speed with 2 sticks in 1 channel (2 sticks in Ch.A only)
2 sticks (in slots 3 and 4) = Single Channel Speed with 2 sticks in 1 channel (2 sticks in Ch.B only)
2 sticks (in slots 1 and 3) = Dual Channel Speed with 1 stick per channel (1 stick in Ch.A + 1 stick in Ch.B)
2 sticks (in slots 2 and 4) = Dual Channel Speed with 1 stick per channel (1 stick in Ch.A + 1 stick in Ch.B)
4 sticks (in all slots) = Dual Channel Speed with 2 sticks per channel (2 sticks in Ch.A + 2 sticks in Ch.B)

becontroller · Nov 20, 2017

raisonjohn :

becontroller :

You're welcome. But, what do you mean it will not work?? Your processor, the Intel Core i5-7600K, has a maximum dual channel memory:

"Memory Specifications
Max # of Memory Channels - 2"
Source: https://ark.intel.com/products/97144/Intel-Core-i5-7600K-Processor-6M-Cache-up-to-4_20-GHz

Your motherboard, the Msi H270 PC Mate, has a dual channel memory architecture:

"MEMORY CHANNEL - Dual"
Source: https://www.msi.com/Motherboard/H270-PC-MATE/Specification

As said in my previous reply, if a motherboard has 4x SLOTS - it does NOT necessarily mean it has 4 channels. A slot is not synonymous to a channel. In your motherboard's case, it has 4x SLOTS (not channels), but only works in 2x CHANNELS.

To achieve dual channel speeds, you need to plug the 2x RAM sticks on the slots assigned to a specific channel. Typically, Channel A is comprised of Slot 1 and Slot 2; then, Channel B is comprised of Slot 3 and Slot 4.

Using that Msi H270 PC Mate, if you plug:
1 stick (any slot) = Single Channel Speed with 1 stick in 1 channel
2 sticks (in slots 1 and 2) = Single Channel Speed with 2 sticks in 1 channel (2 sticks in Ch.A only)
2 sticks (in slots 3 and 4) = Single Channel Speed with 2 sticks in 1 channel (2 sticks in Ch.B only)
2 sticks (in slots 1 and 3) = Dual Channel Speed with 1 stick per channel (1 stick in Ch.A + 1 stick in Ch.B)
2 sticks (in slots 2 and 4) = Dual Channel Speed with 1 stick per channel (1 stick in Ch.A + 1 stick in Ch.B)
4 sticks (in all slots) = Dual Channel Speed with 2 sticks per channel (2 sticks in Ch.A + 2 sticks in Ch.B)

So the rest 2 ram slots,what are used for ? is a waste of space. Im not understanding this yet.Why the ATX Would have 4 slots if only half can be used?

raisonjohn · Nov 20, 2017

What do you mean "only half can be used"? Technically, it's not a waste of space because all 4 slots CAN still be used. Here are some examples why having 4 RAM slots on a dual-channel motherboard is considered:

ON FUTURE RAM UPGRADE:
If a CPU (and its compatible motherboard) has dual channel memory and only 2 RAM slots, this means you can only plug in 1 stick per channel. So, supposed you got an 8GB RAM kit (2 x 4GB sticks) plugged into those 2 RAM slots, and in the future, you want to upgrade to 16GB RAM, you are now forced to buy a new and costlier 16GB RAM kit (2 x 8GB sticks) because your motherboard only has 2 RAM slots. In this case, you have 16GB of RAM (a new 2x8GB kit) with all 2 RAM slots populated working in dual-channel at 1 stick per channel (note that your original 2x4GB RAM kit cannot be used anymore in this setup due to lack of space/additional RAM slots).

However, if your motherboard has dual channel memory and has 4 RAM slots, and you initially got an 8GB RAM kit (2 x 4GB sticks), you'll spend lesser money in upgrading if you decide to go for 16GB RAM. You would then only need to get another 8GB RAM kit of the same model/brand/timings as the original (lesser expenses), because you have 2 more RAM slots available on your motherboard for the upgrade. In this case, you will have 16GB of RAM (2 sets of 2x4GB) with all 4 RAM slots populated working in dual-channel at 2 sticks per channel.

ON SPACE CLEARANCE ISSUES:
Another benefit of having those extra space/slots is spatial (and airflow) concerns. Some use bulkier CPU air coolers that tend to reach and overlap a RAM slot. Having 4 RAM slots on a motherboard often allows one to use faster dual-channel speeds on Slots 2 and 4 (the farthest slot pairing away from the CPU) even when Slot 1 will be obstructed if using large CPU coolers.

ON AESTHETICS:
Some also prefer to populate all 4 RAM slots (especially if using modules with decorative heat spreaders or modules with LED or RGB lighting), for aesthetic purposes.

Additional note: NOT ALL SLOTS ARE REQUIRED TO BE POPULATED
Know that motherboards offer a lot of optional connectivity (slots, ports, headers, etc.), and, not all are mandatory to be populated for the PC system to work. For example, your H270 PC Mate motherboard has several expansion slots (2x PCIe x16 slots, 3x PCIe x1 slots, and 1x PCI slot). These expansion slots take up a much larger surface area on your motherboard compared to the 2x additional RAM slots in question. More often than not, on a typical budget system, you'd only be plugging in a single GPU on the top PCIe x16 slot -- so you are left with 5x unpopulated/open expansion slots on your motherboard below that GPU.

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