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  • Community Question: What makes a good motherboard?

New B450 - only 8gb of 16gb usable?

burninatortech4

Senior member
Jan 29, 2014
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Issue -
I just purchased a new Gigabyte B450 Aorus M (mATX) motherboard. I'm currently unable to use 8gb of the 16gb installed in the system. The installed ram is F4-3200C14D-16GFX (Gskill 3200mhz DDR4 CL14). Rest of rig description is in my sig.


Observations -
Windows task manager and the BIOS both recognize that 16gb is installed. Windows task manager reports that only 8gb is usable and the other 8gb are "hardware reserved". AIDA64 shows both sticks but provides a full read-out on only one of the sticks.

My first assumption was a bad ram stick but I've observed the following while trying to troubleshoot:

1) the system fails to boot with only one stick installed (regardless of channel A/B). The system boots in both channel A/B but the issues remains

2) both sticks respond normally in both my AB350N-WIFI ITX system and worked fine in my old B350 system. I just verified the sticks are good prior to posting this.

3) the same issue arises when I pulled the RAM (8gb DDR4 2400mhz) out of my AB350N-WIFI and put in the same slots as my Gskill memory; only half of the ram is usable.

4) Reinstalling windows or BIOS reset (including pulling battery) don't fix the issue.
Do I have a bad memory channel? What is going on here? If it seems unfixable I'd like to do a prompt return.
 
Last edited:

VirtualLarry

Lifer
Aug 25, 2001
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It sounds like the mobo has a bad memory slot or something. I would strongly consider returning it.
 

UsandThem

Elite Member
Super Moderator
May 4, 2000
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That RAM isn't on Gigabyte's QVL list, so it could be something as simple as that. Ryzen chipsets are a lot more finicky about RAM, so buying RAM on their QVL list is a must IMO.

You can rule out the bad stick / bad slot by testing out each one separately, in different slots.
 

VirtualLarry

Lifer
Aug 25, 2001
49,543
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That RAM isn't on Gigabyte's QVL list, so it could be something as simple as that. Ryzen chipsets are a lot more finicky about RAM, so buying RAM on their QVL list is a must IMO.

You can rule out the bad stick / bad slot by testing out each one separately, in different slots.
But even if the RAM isn't on the QVL, it should still work at the basic Jedec speeds, without XMP enabled. (DDR4-2133)

If it won't work even at Jedec speeds, something is broken.
 
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UsandThem

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But even if the RAM isn't on the QVL, it should still work at the basic Jedec speeds, without XMP enabled. (DDR4-2133)

If it won't work even at Jedec speeds, something is broken.
Could be. But I've seen some QVL lists where they say only one module will work (usually two modules work just fine).

I'd recommend he test each stick separately, in each slot before sending back the motherboard for a replacement. The problem is going to be either:

A. RAM module defective
B. Memory slot defective
C. Compatibility problem

Running Memtest on each module should see if it is the first two possibilities.
 

UsandThem

Elite Member
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I missed his quoted text (had to expand it) since I'm on mobile where they tried different RAM and had the same issue.

So I would say it's likely the motherboard that is defective.
 
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VirtualLarry

Lifer
Aug 25, 2001
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Could be. But I've seen some QVL lists where they say only one module will work (usually two modules work just fine).
Only one module will work? That makes NO sense. Maybe 1DPC (one DIMM per channel). But these are dual-channel CPUs, therefore, there's no reason that one DIMM would cause "interference" with the second channel, at least that I know of.
 

vailr

Diamond Member
Oct 9, 1999
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Looking at the user manual, 2x sticks of memory should be placed either in: slots 1 + 2, or slots 3 + 4.
Which is different than what is recommended for Intel CPU board memory placement: 1 + 3, or 2 + 4.
Also: that specific memory model number is not on their QVL list.
There's a good chance that a system firmware bios update would resolve the issue, but only the initial bios version is listed for download, as of now.
 
Last edited:

UsandThem

Elite Member
Super Moderator
May 4, 2000
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Only one module will work? That makes NO sense. Maybe 1DPC (one DIMM per channel). But these are dual-channel CPUs, therefore, there's no reason that one DIMM would cause "interference" with the second channel, at least that I know of.
It's usually much larger sticks and not the smaller capacity ones. Like I mentioned in that same post, most of the time the minimum number listed as working is two modules (with some modules working with all four slots populated).
 

burninatortech4

Senior member
Jan 29, 2014
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Thanks for all your advice. The motherboard decided to suddenly start working (both the full 16gb and 3200mhz). I can't really explain why.
 

Ketchup

Elite Member
Sep 1, 2002
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Sounds like the UMA frame buffer option was allocating memory. Glad you got it straightened out.
 

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