Question confusing memory issue

[JCharlesR]

Hello.

I have a PC with a Gigabyte GA-P55A-UD3 motherboard, with 8GB of Corsair XMS3 RAM. It's been running in this configuration (windows 7 pro) for several years with no issues.

The other day I decide to add more RAM. Per the MB documentation, the board can take up to 16GB of memory. So I buy two 4GB sticks, all the same specifications as the "original" sticks. Each stick is 4GB (2x2GB), DDR3, same frequency, same voltage, same Corsair part number.

I power off, put the two stick in and start it up. No luck. Once it gets to "Starting Operating System..." it either locks up or reboots. Cleared CMOS and selected fail-safe settings. Still no luck! So, I pull out all the memory but one stick, which should leave me with 4GB (each stick is 4GB). I start it up and it boots. I look at the installed memory under computer properties, it shows 2GB, not 4.

I throw in another stick, which should leave me with 8GB of memory. Windows sees only 4GB.

Is there something I'm not getting??? Shouldn't the system recognize the memory, or do I have to make some sort of adjustment in BIOS?

Thanks!

John

 

[alceryes]

Memory not purchased as a kit is not guaranteed to work with any other memory - even if it's the same brand/model.
Just guessing, but I would say that the newer memory is high density which your board either doesn't support or only supports in 2 or less modules (not fully populated).
If you take out the new memory and put the old memory in the same slots they were in before do you get your 8GBs back?

 

[JCharlesR]

No, I don't get my 8GB back, but I may not have had it in the first place

When I put this system together maybe 6 or 7 years ago, I only bought two sticks (4GB each) of memory for it. At the time I don't even think I looked to see if BIOS or Windows was showing that much memory.

I did determine that I do have a bad memory slot. Regardless of if I put an old or new stick in slot #1, the PC refuses to do anything but beep and reboot itself, over and over. Blew it out with air, inspected it, am positive the memory is seating correctly, but the PC does not like anything in that slot.

While that's unfortunate, I'm left to wonder why BIOS and Windows only shows half the memory that is installed. Right now it shows 6GB, while it has 12GB installed. If I pull one stick out, it shows 4GB when there is actually 8GB in it, and so on, and that's regardless of if the memory I put in is "new" or "old".

Looking at BIOS, I don't see that any method exists to toggle memory on or off, but then I'm no expert.

 

[alceryes]

It may not be a bad slot.
A lot of newer boards have a certain order that memory slots need to be populated. Depending on the board, some require the second and fourth to be populated before the first and third. Your manual should give the details. Combine this with the fact they you may be using high density RAM in a low density only board and it could explain the weirdness you are experiencing.

 

[JCharlesR]

And right you are! I pulled all the RAM, and put one stick in slot one only. Booted fine, no complaints. It still shows 2GB instead of 4, but at least the slots not bad. So I put the remaining sticks back in and it shows 8 instead of 16GB. The reason I now suspect is because the RAM isn't on the Gigabyte supported RAM list. How I ended-up buying non-supported RAM in the first place was just my ignorance I suppose.

Thanks much.