Question Corsair - Memory Clock Speeds - AMD 7950x Information Req

[HJW001]

Hi All,

Can someone help me explain how memory works in regard to my new PC build?

I have checked the ram clocked speed and it shows the below.

Default clock speed - 2400Mhz.
Current Clock Speed - 1800Mhz

I have tried changing the bios to XMP but it keeps freezing and rebooting, I know it won't get to the 6400Mhz but thought it would be higher than the above.

I have the below specs.

CPU: AMD 7950x
RAM: x4 - 32gb Corsair Vengance 6400Mhz (128gb total) overkill I know....
M/B - Gigabyte Aorus Master x670e
PSU - 1000w MSI


Cheers

 

[Darkbreeze]

Download HWinfo. Install it. Run it. Choose "Sensors only". Scroll down to the memory section and take a screenshot. Install CPU-Z. Take screenshots of both the SPD and memory tabs. On the SPD tab you will need to select each of the DIMM slots you have populated with memory and take a separate screenshot so we can compare each DIMM. Use the instructions at the following link to post the screenshots here.

How to PROPERLY post images on the Tom's hardware forum


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[HJW001]

Hi Darkbreeze,

Thanks for the info, hopefully this will be enough for some answers

Cheers

 

[Darkbreeze]

The speed you see in HWinfo, 1800mhz, is HALF the actual speed it's running at, which is 3600MT/s. Actual speed is Mhz but modern consumer memory (DDR3, DDR4, DDR5) is "double data rate" which means there is double the throughput. Not double the frequency, but double the throughput, so double DATA rate. Exactly like on the SPD tab screenshot of the XMP profile where it shows 3200Mhz below the XMP-6400 header. 6400MT/s (Mega transfers per second, which is the correct terminology for the actual advertised throughput) is double the frequency of 3200.

However, since yours is showing 1800Mhz in HWinfo, meaning 3200MT/s, which is not possible really with DDR5 since the lowest supported native speed is 4800MT/s.

To begin with, basically ALL Ryzen systems, from Gen1 through Gen 5, for the most part do not like Vengeance memory kits. So that's one strike against you right there.

Secondly, most users don't realize that on Ryzen systems if you populate all four DIMM slots you typically see a pretty major speed reduction, and this happens anytime you have DIMMs installed in both the A and B channels. For best speed, you want only two DIMMs, in the A2 and B2 slots. So if you want 128GB, you are MUCH better off with a 2 x64GB kit, and I highly recommend looking at either G.Skill Ripjaws or Trident kits (Of which there are AMD specific series to improve compatibility, but you still want to check the G.Skill memory finder or the QVL list for your motherboard to verify compatibility).

Thirdly, your memory kit does not seem to be on either the Corsair memory finder utility OR the QVL list for your motherboard, which means while it CAN work in some cases, it is usually either problematic or impossible. Especially without a great deal of tweaking of the timings, voltage, etc. and for most people if they were comfortable with doing that they wouldn't be here asking questions to start with.

I'd recommend a different memory kit and I'd recommend you either don't go with that much memory because there is practically very little chance you will ever use even half that anyhow, or understand that it's unlikely you are going to see those speeds. Also, for Ryzen 7000 series platforms, 6000MT/s is the highest speed most users will see, using two DIMMs, without paying an infinity fabric penalty which might also be why you are seeing such low speed.

You could try manually setting your memory speed to 6000MT/s in the BIOS and use the default timings and voltage to begin with, but there are no guarantees when using four DIMMs on these platforms. Also, you did not provide a screenshot of the Memory tab in CPU-Z.