Question AMD Ryzen 5 3600X - RAM Slots A1+B1 run at reduced speed on ASUS Motherboards?

Jul 12, 2020
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Hey folks,

I've been testing the AMD Ryzen 5 3600x CPU on two different ASUS motherboards and have come to the conclusion that it is incapable of running RAM at full speed in slots A1+B1.
It can only run at full speed in slots A2+B2.

Here are the motherboards I've tested:
ASUS ROG STRIX B450-F GAMING
ASUS TUF B450-PLUS GAMING AM4

Here are the RAM models I tested (always tested separately with same RAM model, never mixed):
G.SKILL Trident Z RGB (For AMD) 16GB (2 x 8GB) 288-Pin DDR4 SDRAM DDR4 3600 (PC4 28800) Desktop Memory - Model F4-3600C18D-16GTZRX
TeamGroup T-FORCE VULCAN Z 32GB (2 x 16GB) DDR4-3200 PC4-25600 CL16 Dual Channel Desktop Memory - Model TLZGD432G3200HC

Here are my results:
G.SKILL - slots A1+B1 - 2133MHZ
G.SKILL - slots A2+B2 - 3600MHZ
G.SKILL - slots A1+A2+B1+B2 - 2133MHZ
Teamgroup - slots A1+B1 - 2400MHZ
Teamgroup - slots A2+B2 - 3200MHZ
Teamgroup - slots A1+A2+B1+B2 - 2400MHZ

Is this a limitation of the AMD Ryzen 5 3600x CPU or with ASUS motherboards?
 

4745454b

Titan
Moderator
Did you check any settings in the bios? If all you did was plug them in and check, you should see if XMP or whatever AMD calls it needs to be on. I could see the first slots needing to run anything that's plugged in so that if/when low end ram is used it's not trying to run them too fast.

I'm using a Gigabyte board and 3200MHz DDR4 ram. I don't remember, but I think it defaulted to 2400MHz. I enabled XMP and rebooted and it was running at 3200. It's not a limitation of anything, just a setting that needs to be enabled. Or improved if you feel it should be automatic.
 

Math Geek

Champion
Ambassador
same for me. i had to enable XMP to get full speed. think it defaulted to 2600 but then has run no problem at 3200 since XMP enabled.

never had a reason to test it in other slots or other boards since it worked right away the first time.

i'm also running a GB board. B450 aorus pro wifi for me
 
Jul 12, 2020
7
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Did you check any settings in the bios? If all you did was plug them in and check, you should see if XMP or whatever AMD calls it needs to be on. I could see the first slots needing to run anything that's plugged in so that if/when low end ram is used it's not trying to run them too fast.

I'm using a Gigabyte board and 3200MHz DDR4 ram. I don't remember, but I think it defaulted to 2400MHz. I enabled XMP and rebooted and it was running at 3200. It's not a limitation of anything, just a setting that needs to be enabled. Or improved if you feel it should be automatic.
Yes, sorry I forgot to mention, I needed to enable D.O.C.P to get it to run on full speed on slots A2+B2, however D.O.C.P had no effect on slots A1+B1.
I also tried rebooting several times, enabling and disabling D.O.C.P, switching back and forth between Optimized Defaults and D.O.C.P but nothing will get slots A1+B1 to run at full speed.
 
Jul 12, 2020
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same for me. i had to enable XMP to get full speed. think it defaulted to 2600 but then has run no problem at 3200 since XMP enabled.

never had a reason to test it in other slots or other boards since it worked right away the first time.

i'm also running a GB board. B450 aorus pro wifi for me
I don't see an XMP setting on either of these motherboards, only D.O.C.P, but I think they do something similar.
D.O.C.P enabled does help with slots A2+B2 run at full speed but has no effect on A1+B1

Can I ask what slots you are using on your motherboard?
 
I don't see an XMP setting on either of these motherboards, only D.O.C.P, but I think they do something similar.
D.O.C.P enabled does help with slots A2+B2 run at full speed but has no effect on A1+B1

Can I ask what slots you are using on your motherboard?
DOCP is Asus's name for XMP it's same thing. XMP is in the RAM control chip and invented by Intel. It's set of instructions to BIOS to set itself to get maximum tested performance of memory, some would call it overclock.
Normal slots for that MB is A2 and B2 for 2 sticks but you are using two different sets of RAM and that's difficult to make work. At best all would work at speed of slower one.
That's why RAM should not be mixed but all should be in same set. Memory controller is in CPU itself and has two channels but it's only one controller so it can't handle different speeds at same time so it sets them at their minimal speeds. Only server CPUs have multiple and independent memory controllers, ordinary CPUs don't.
 
Reactions: GarrettL
Jul 12, 2020
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DOCP is Asus's name for XMP it's same thing. XMP is in the RAM control chip and invented by Intel. It's set of instructions to BIOS to set itself to get maximum tested performance of memory, some would call it overclock.
Normal slots for that MB is A2 and B2 for 2 sticks but you are using two different sets of RAM and that's difficult to make work. At best all would work at speed of slower one.
That's why RAM should not be mixed but all should be in same set. Memory controller is in CPU itself and has two channels but it's only one controller so it can't handle different speeds at same time so it sets them at their minimal speeds. Only server CPUs have multiple and independent memory controllers, ordinary CPUs don't.
Just want to clarify, I’m not mixing the G.skill and Teamgroup RAM. I ran each test with identical RAM in each set (see test results above).
Regarding the point about A2 and B2 being the normal slots for 2 sticks, does that mean I am unable to run 4 sticks at full speed because the motherboard or CPU is reducing the speed for A1 and B1?
 
Just want to clarify, I’m not mixing the G.skill and Teamgroup RAM. I ran each test with identical RAM in each set (see test results above).
Regarding the point about A2 and B2 being the normal slots for 2 sticks, does that mean I am unable to run 4 sticks at full speed because the motherboard or CPU is reducing the speed for A1 and B1?
Yes, that's one reason and the other one is that using both channels at same time even when they are identical, coming in same set, places more load on controller and in Ryzen's case it's mostly limited to 3200MHz. It's also up to particular memory's JEDEC and XMP as well as up to BIOS for it's defaults. You may get some better results by using https://www.techpowerup.com/download/ryzen-dram-calculator/ to help you with manual settings.
http://www.softnology.biz/files.html would help you find finer details about your RAM to enter in Dram calculator.
 
Hey folks,

I've been testing the AMD Ryzen 5 3600x CPU on two different ASUS motherboards and have come to the conclusion that it is incapable of running RAM at full speed in slots A1+B1.
It can only run at full speed in slots A2+B2.

Here are the motherboards I've tested:
ASUS ROG STRIX B450-F GAMING
ASUS TUF B450-PLUS GAMING AM4

Here are the RAM models I tested (always tested separately with same RAM model, never mixed):
G.SKILL Trident Z RGB (For AMD) 16GB (2 x 8GB) 288-Pin DDR4 SDRAM DDR4 3600 (PC4 28800) Desktop Memory - Model F4-3600C18D-16GTZRX
TeamGroup T-FORCE VULCAN Z 32GB (2 x 16GB) DDR4-3200 PC4-25600 CL16 Dual Channel Desktop Memory - Model TLZGD432G3200HC

Here are my results:
G.SKILL - slots A1+B1 - 2133MHZ
G.SKILL - slots A2+B2 - 3600MHZ
G.SKILL - slots A1+A2+B1+B2 - 2133MHZ
Teamgroup - slots A1+B1 - 2400MHZ
Teamgroup - slots A2+B2 - 3200MHZ
Teamgroup - slots A1+A2+B1+B2 - 2400MHZ

Is this a limitation of the AMD Ryzen 5 3600x CPU or with ASUS motherboards?
Yes.
 

TFBundy

Distinguished
May 1, 2008
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This is the expected behaviour in most modern systems due to memory topology. If you have sticks only in slots A1 / B1 you will have an unterminated trace, so impedance and transients will be all over the place, when you put them in slots A2 / B2 the sticks act as terminators. Some high quality 4 piece matched kits will let you get reasonable clocks, but you will pay for it through the nose.
Essentially, look for workstation grade boards if you want high memory density.

This should get you started, if you want to fall down this rabbit hole.
 
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