8GB RAM modules on Asus Sabertooth 990fx

memory

I got an Asus Sabertooth 990fx tonight, but I've been unable to get it to POST with my 8GB memory modules (Kingston KTD-PE310Q8, ECC Registered, 1066, 8GB each for 16GB total).

The box and manual says it supports up to 32GB total, and there's only 4 slots, so it must take 8GB sticks. Has anyone gotten this motherboard working with 8GB sticks and can confirm that?

Is it the 8GB that's causing the problem or the fact that the memory I'm using is registered? It says it supports ECC and I want that as this will be a server. But I don't need it to be registered.

There's also a very limited selection of 8GB sticks, even online- will server RAM work?

Best Answer

Page 24, section 2-6 of the manual, found at the Asus Site state:

You may install 1GB, 2GB and 4GB unbuffered and non‑ECC DDR3 DIMMs into the DIMM sockets.

...which is odd, because it also says:

4 x DIMM, Max. 32GB, DDR3 1866/1600/1333/1066 MHz, ECC, Non-ECC and un-buffered memory Dual channel memory architecture

Shame, because it's a nice board.

Related Solutions

Memory specs say “4 x DIMM Max. 32GB DDR3” – what does this really mean

This means your motherboard accepts up to 32GB of memory. The BIOS is designed to allow up to 32GB, but has not been formally tested for this amount of memory.

If you are running Windows, make sure you are running Windows 7 Professional or Ultimate 64-bit (Home Premium can only accept 16GB), and as C2940680 noted, you may want to disable or manually limit the size of the pagefile, as it will be very large by default. Recent Linux kernels should have no trouble accessing this amount of memory.

Windows 10 seeing but ignoring one RAM slot

There could be a few reasons why your memory isn't usable.

First things first:

It's not a good idea to mix-and-match your RAM, different sizes and vendors.
- It can lead to system instability
- In your case, you will encounter decreased performance (even if you do get the extra memory mapped) because you will not benefit from a dual-channel configuration see: What is dual channel memory?
- If you do mix and match ALWAYS do it in pairs.

Note, that the color-coding on your motherboard RAM slots is not just for "kicks", the color pairing are the two channels (A and B) that your motherboard owners manual refers to. If you do install different sized RAM chips, do it in pairs, matching the Channel with the set. This is probably the #1 reason why it's not usable to your system.

A quick way to test my theory would be to remove the other smaller 4GB stick in the matching color of the 8GB stick and try to boot your system. If all goes well, you'll now see 16GB usable, instead of 12GB. If so, then your best option is to buy another of the 8GB sticks (same brand and model). You should then be able to use that full 24GB.

The owners manual of your motherboard states:

You may install varying memory sizes in Channel A and Channel B. The system maps
the total size of the lower-sized channel for the dual-channel configuration. Any excess
memory from the higher-sized channel is then mapped for single-channel operation.

I also want to point out that the RAM you have is not listed in your motherboard's Qualified Vendors Lists (QVL). While this is not an exhaustive list of RAM that is compatible with your MB, it is a list that signifies what was tested with your MB. Going out of these bounds is more of an "at your own risk" sort of grounds.

Windows also has some reasons as to why it may not be mapped (for 7, but it should still apply to 10 as well): https://support.microsoft.com/en-us/help/978610/the-usable-memory-may-be-less-than-the-installed-memory-on-windows-7-b

Best Answer

Related Solutions

Memory specs say “4 x DIMM Max. 32GB DDR3” – what does this really mean

Windows 10 seeing but ignoring one RAM slot

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