X399 Phantom Gaming 6 + Corsair RAM = Only 50% Fun

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   Hi there,

I have a problem with my X399 Phantom Gaming 6 Motherboard. I have installed 4 bars of Corsair Vengeance Pro with 16GB (2x8GB) each. Their SKU is CMW64GX4M4E3200C16. My CPU is a Threadripper 2920x.

I did a CMOS reset and loaded the UEFI defaults afterwards.

The RAM bars are placed in the recommended slots A2, B2, C2 and D2. They are all recognized in BIOS/UEFI, but only with half of their memory size (8192MB each) and a clock speed of 2133MHz instead of 3200MHz. While I can set the XMP 2.0 profile 1 in order to adjust their speed to 3200MHz, I cannot make the board detect the correct memory size of 16GB each, so 64GB in total.

What could I try to fix this?

Thanks guys, I am a pretty desperate noob and want to excuse myself in case this is a well-known problem to experts. 

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Troy Members Profile Send Private Message Find Members Posts Add to Buddy List Newbie Joined: 09 May 2021 Status: Offline Points: 65	Post Options Post Reply Quote Troy Report Post Thanks(0) Quote Reply Topic: X399 Phantom Gaming 6 + Corsair RAM = Only 50% Fun Posted: 09 May 2021 at 6:08pm
	Hi there, I have a problem with my X399 Phantom Gaming 6 Motherboard. I have installed 4 bars of Corsair Vengeance Pro with 16GB (2x8GB) each. Their SKU is CMW64GX4M4E3200C16. My CPU is a Threadripper 2920x. I did a CMOS reset and loaded the UEFI defaults afterwards. The RAM bars are placed in the recommended slots A2, B2, C2 and D2. They are all recognized in BIOS/UEFI, but only with half of their memory size (8192MB each) and a clock speed of 2133MHz instead of 3200MHz. While I can set the XMP 2.0 profile 1 in order to adjust their speed to 3200MHz, I cannot make the board detect the correct memory size of 16GB each, so 64GB in total. What could I try to fix this? Thanks guys, I am a pretty desperate noob and want to excuse myself in case this is a well-known problem to experts.

Troy Members Profile Send Private Message Find Members Posts Add to Buddy List Newbie Joined: 09 May 2021 Status: Offline Points: 65	Post Options Post Reply Quote Troy Report Post Thanks(0) Quote Reply Posted: 09 May 2021 at 6:13pm
	Update: My BIOS/UEFI Version is 1.31 (latest)

Troy Members Profile Send Private Message Find Members Posts Add to Buddy List Newbie Joined: 09 May 2021 Status: Offline Points: 65	Post Options Post Reply Quote Troy Report Post Thanks(0) Quote Reply Posted: 10 May 2021 at 1:08pm
	Thread can be closed. Turned out that I was misled by the labels on the memory bars. They show the size of the KIT, not the size of the bar.

Xaltar Members Profile Send Private Message Find Members Posts Add to Buddy List Moderator Group Joined: 16 May 2015 Location: Europe Status: Offline Points: 22793	Post Options Post Reply Quote Xaltar Report Post Thanks(0) Quote Reply Posted: 10 May 2021 at 5:10pm
	I was about to say are you sure they are 16gb modules :) I am glad you are all sorted. I have the same board paired with a 2950x, 2 years in and it's still running flawlessly. Enjoy :)


Troy Members Profile Send Private Message Find Members Posts Add to Buddy List Newbie Joined: 09 May 2021 Status: Offline Points: 65	Post Options Post Reply Quote Troy Report Post Thanks(0) Quote Reply Posted: 10 May 2021 at 5:14pm
	Hi Xaltar, thanks for your answer. While I now know the correct size, I noticed some issues with the speed and have it now set to 2666MHz. Do you have the RAM running at 3200 MHz? I experienced some BSODs with this speed and with 3000 MHz. Anything board specific I have to set up? Do I need the DRAM calculator trickery?

Xaltar Members Profile Send Private Message Find Members Posts Add to Buddy List Moderator Group Joined: 16 May 2015 Location: Europe Status: Offline Points: 22793	Post Options Post Reply Quote Xaltar Report Post Thanks(0) Quote Reply Posted: 11 May 2021 at 3:16am
	You will likely need to use DRAM calc. I got lucky with mine, my RAM is Samsung B-Die based so it worked right out of the box @3600 once I enabled XMP. Several other kits I have tried did not work with XMP though and required manual settings using DRAM Calc.