CPU supporting four-channel DDR4 RAM

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dwevans427

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Kind of a silly question, maybe very simple to answer. My processor is an intel 5820k-v3, on the box it clearly says it supports "four-channel DDR4 RAM." Yet I have two sets of 16 gig 2133 MHz RAM (8 x 4).

If I install eight sticks of RAM, does the frequency get cut in half for each stick?

If so, does using XMP profile still benefit anything, and is performance going to be lost due to cutting the frequency in half?
 
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thor220
The RAM won't run at the rated speed unless you turn the XMP profile in the BIOS. Just as a note, the XMP profile must overclock your memory controller in order to obtain those speeds as they are outside Intel's specifications. Your motherboard is very good so I'm sure you won't have an issue.
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thor220

thor220

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The thing with Quad Channel RAM is that it isn't guaranteed to work unless you buy a quad channel kit. As you have two dual channel kits, there's a chance they won't work in dual channel mode. In addition, you cannot use XMP profiles from a dual channel kit on a quad-channel setup. For that you need a quad-channel kit that comes with XMP profiles designed to work with quad channel. Just ignore XMP entirely.
 
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synphul

synphul

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The frequency doesn't get cut in half. Using ram in quad channel means it can access 4 sticks simultaneously, broader data paths between the cpu and the ram.

The xmp profile is to run ram at it's advertised speed when it exceeds 'standards'. That cpu is listed to handle ram up to 2133 so chances are the ram being 2133 should automatically run at full speed. If it tries to run at a lower speed like 1333 or 1600 then simply enable the xmp profile to set the ram to run at 2133 at the timings listed on the package.

You're not losing ram capacity or speed by running in quad channel though, nor are you losing capacity.
 
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N3rdR4ge

N3rdR4ge

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i'm pretty certain he is saying he has two quad channel kits. frequency will not be cut in half. the only thing that will drop your frequency is using different speed sticks. they will adjust to the slowest one. xmp profile should work fine as long as all 8 are the same sticks.
 
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joex444

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They said they have two sets of 16GB (8x4GB). Two sets yielding 8 sticks must be each set is 4 sticks, meaning they're quad channel sets so any of this dual vs quad kit XMP stuff just doesn't matter.
 
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joex444

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A single module is able to access 64-bits at a time, this is the "width." A dual channel configuration is configured such that it accesses 128-bits at a time. Now, "at a time" means "in one clock cycle." Clearly if you run 64-bit accesses at 1 billion times per second that's like running 128-bit accesses 500 million times per second (ie, 1GHz 64-bit is like 500MHz 128-bit... is like 250MHz 256-bit).

All quad channel does is make it access 256 bits at a time. That's it. Because that's all it is, it doesn't mess with frequency. So, no, quad channel or even all 8 modules at once doesn't mean the frequency is halved. If it did there would be no point because you could use them at their full speed with 128-bit access width and get the same bandwidth. The entire point of dual or quad channel is to improve bandwidth.

Actually, this is pretty much like RAID0 except for RAM. With RAID0, you access a 100MB file as two 50MB reads across two disks. With dual channel you'd access a 100MB read from memory as 50MB from two modules, and with quad channel its four 25MB reads. This is why the bandwidth can go up so drastically (DDR4 on X99 with 4 DIMMs is capable of 50-60GB/s, while dual channel is in the 20-30GB/s range, and single channel can be under 10GB/s... especially on AMD platforms).
 
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thor220

thor220

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Are you guys sure about that?

"two sets of 16 gig 2133 MHz RAM (8 x 4)"

A quad channel kit of 8 GB x 4 sticks would be 32 GB, not 16 GB.
 
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dwevans427

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The XMP profile under a 15 minute stress test works fine. It's two sets of identical 4 X 4 Gig RAM.

Please read my question and answer it as opposed to telling me what to do
 
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dwevans427

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The reason I asked the question In the first place is because cpuid is reporting 1066 MHz speed ram and I figured the frequency got cut in half because the CPU wants four sticks of RAM. The motherboard is x99 Sabertooth.

What is CPU-id referring to?
 
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thor220

thor220

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The RAM won't run at the rated speed unless you turn the XMP profile in the BIOS. Just as a note, the XMP profile must overclock your memory controller in order to obtain those speeds as they are outside Intel's specifications. Your motherboard is very good so I'm sure you won't have an issue.
 
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