DRAM confusion - PC4-21300 vs PC4-25600 (resolved)

[Gorlash]

I am confused about what speed my DRAM is, in my new system...

motherboard: ASUS TUF GAMING X570-PLUS (WI-FI)
cpu: AMD Ryzen 7 3700X
memory: 4*8GB Corsair CMK16GX4M2Z3200C16

Both Amazon and Corsair say that this memory is PC4-25600/DDR4-3200,
but now that I have them installed, both HWINFO64 and CPU-Z say that it is PC4-21300/DDR4-2666 ...
Yet HWINFO64 shows the correct Corsair part number...

Why is this happening?? and is there any way that I can fix this??

 

[drescherjm]

Why is this happening??

The RAM chips are probably JEDEC DDR4-2666 but the manufacturer of the module tested them at the overclocked speed.

To achieve this speed you need to enable memory overclocking in your motherboard

A quick google returned the following instructions to enable memory overclocking:

1. Open the bios menu by clicking the “F2” or “Del” button while starting or restarting the PC.
2. Go to advance mode.
3. Select AI Tweaker/Overclocking tab.
4. Select AI Overclocking Tuner to Manual/XMP(Extreme Memory Profile)

 

[Gorlash]

Oh, interesting...
Yes, I also found a site that talked about the BIOS setting in AI Tweaker... I went there, and set that DRAM speed to 3200Mhz... supposedly that is all that is required??

The motherboard manual actually hinted at this; under Memory, it has this entry (shown in included image)

)...

Note that all speeds above 2666 say (O.C.)...

So I did this, and rebooted, and now CPU-Z shows memory clock as 1600Mhz... but all entries about the DRAM chips still say DDR4-2666....
I guess that means that drescherjm is correct, and the chips are *really* the lower speed... which is sort of a drag, considering that I paid for DDR4-3200...
So I'm really not sure what I'm actually getting at this point...

 

[pitingres]

If CPU-Z is showing the memory clock as 1600 MHz, you're running at 3200 MT/s, which is the speed you paid for. The other places where it says DDR4-2666 are probably reading the SPD info which is the base rate. The DDR4 standard (JEDEC) doesn't recognize speeds over 2666 MT/s, as I understand it, which is why all the higher speeds are marked as overclocked speeds.

You'll note that I said 3200 MT/s, which is million transfers per second. DDR memory transfers twice per clock (Double Data Rate), so a clock of 1600 MHz gets you 3200 million transfers per second. Yes, everyone calls it MHz, which is infuriating because it's simply wrong, but we're stuck with it. I guess the memory and mobo makers think we're too stupid to understand another unit of measurement.

(If the memory were running at the non-XMP rate of DDR4-2666, 2666 MT/s, the CPU-Z memory clock speed would be listed as 1333 MHz.)

 

[Gorlash]

If CPU-Z is showing the memory clock as 1600 MHz, you're running at 3200 MT/s, which is the speed you paid for. The other places where it says DDR4-2666 are probably reading the SPD info which is the base rate. The DDR4 standard (JEDEC) doesn't recognize speeds over 2666 MT/s, as I understand it, which is why all the higher speeds are marked as overclocked speeds.

You'll note that I said 3200 MT/s, which is million transfers per second. DDR memory transfers twice per clock (Double Data Rate), so a clock of 1600 MHz gets you 3200 million transfers per second. Yes, everyone calls it MHz, which is infuriating because it's simply wrong, but we're stuck with it. I guess the memory and mobo makers think we're too stupid to understand another unit of measurement.

(If the memory were running at the non-XMP rate of DDR4-2666, 2666 MT/s, the CPU-Z memory clock speed would be listed as 1333 MHz.)

Okay, that's good... I understand... Thank you for the info on the JEDEC DDR4 standard, that's something that I didn't know *anything* about!!

Also, I just ran Sandra memory benchmarks, and it confirms that memory is running at 3200Mhz (yeah, I know that the actual clock is half that!! )...
So I am content now...

Thank you all for your advice!!

 

[owcraftsman]

To find the approx data rate divide by 8. some are rounded up and other down similar to 1 TB hard drives some are called that but only have 960GB vs 1024GB (actual 1TB)
Because a modules peak transfer rate is calculated by taking transfers per second and multiplying by eight the reverse is true to calculate rated speed.
25600/8=3200. ( 25600 being the max theoretical transfer rate ) (3200 being the rated speed or transfers per second)
21300/8=2662.5 or 2666
I would say the modules are 3200
Motherboards have a default supported value that they default to all else is considered overclocking or underclocking, so when you enable the XMP timing in bios it is an overclock according to the mobo but that does not make the memory 2666. The motherboard is overclocking in the sense that it is now running at above it's default. I think the motherboard manufacturers do this so they are not responsible for anything more than what they have rated it to operate at. Don't call me when it doesn't work call your memory supplier. This is why folks consult the specific motherboard qualified vendors list before making a memory purchase.

Your Mobo Qualified Vendors List
Found Here

 

[pendragon1]

yup, its just at, and reading, the default jdec speed. turn on xmp and set them to 3200. if there is any instability, up the voltage to 1.4v(its safe). every set of corsair ram ive used needed more voltage.