RAM Only Works in B Slots

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avcomtechsvc

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Oct 22, 2015
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I built a new system using an ASUS Z-97 Pro Gamer Motherboard. I bought 2 sets of CORSAIR Vengeance Pro 16GB (2 x 8GB) 240-Pin DDR3 SDRAM DDR3 2400 (PC3 19200) RAM (32G total).

The RAM will not post in the A slots. It posts fine in the B slots, but I can only use 16G of RAM. I've tried both sets of RAM with the same result. I just replaced the MB with a new one from ASUS and it does the same.

So the PC works fine except RAM only works in single-channel mode and I can't use all my RAM. Since the RAM works fine in the B slots the RAM doesn't appear to be the problem. I'm stumped.
 
Solution
Tradesman1
What's your CPU cooler? If third party like a 212 EVO, H7 or whatever, try loosening it up and tighten down screw tight - if too tight in a corner or side it can throw the MC (memory controller) off. What's the DRAM model #?

Also Ganged-Unganged is an AMD thing - you have an Intel mobo. XMP is programmed to the packaged set so your 2 stick packaged won't have the advanced timings that a 4 stick set will want - enabling XMP will be hoping the BIOS itself can make adjustments.. and lastly what CPU? Good chance you'll need to OC the CPU a bit to even think of running 4 sticks at 2400.
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Shaun o

Shaun o

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Oct 7, 2007
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So both of the 2 x 8GB kits match in every way.

Speed, timing values, and voltage. Check both sets of memory kits for any values that differ.

Ok well there are a few things in the bios you may have to tinker with.
First of all is any memory hole remapping option should be enabled.

The second is how the memory is set, you may have an option in the bios that says memory mode.
Ganged and un Ganged.

Since you have four sticks of memory it needs to be set to Ganged.

When you have two sticks of memory in the board, go into the bios and look for these settings.
You also want to enable XMP mode on the memory. Partly because in most cases without it set the voltage the board gives the dims 1.5v and xmp feeds 1.65v.

And cause when two kits are installed booting and memory detect problems if not pre set to Xmp enbled modes.

Once you have set all of the options.
Save them before you exit the bios.
Shut the system down.

And place the other two 8Gb memory sticks in the free sockets of the board.
And see if it boots with all four and reading 32Gb.
 
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Tradesman1

Tradesman1

Legenda in Aeternum
Jun 5, 2013
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What's your CPU cooler? If third party like a 212 EVO, H7 or whatever, try loosening it up and tighten down screw tight - if too tight in a corner or side it can throw the MC (memory controller) off. What's the DRAM model #?

Also Ganged-Unganged is an AMD thing - you have an Intel mobo. XMP is programmed to the packaged set so your 2 stick packaged won't have the advanced timings that a 4 stick set will want - enabling XMP will be hoping the BIOS itself can make adjustments.. and lastly what CPU? Good chance you'll need to OC the CPU a bit to even think of running 4 sticks at 2400.
 
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