Only 16 of 32 GB recognized - XPS 8500, i7-3770, Win7 Professional...

Have you tried clearing BIOS?

1. Open BIOS setup and copy down all the current settings
2. Power off and unplug
3. Press/hold power botton for ~15 sec
4. Open case and remove motherboard battery
5. Press/hold power button for ~30 sec
6. Reinstall battery (right-side-up!)
7. See if BIOS recognizes all RAM now

NOTE: After you reset BIOS to the defaults, if you get any error messages or other odd behavior, open BIOS setup and confirm the settings match what you wrote down or change them to match what you wrote. Be sure to save any changes before exiting setup.

RoHe,

Thank you for your suggestion.  No, I have not attempted the steps that you just detailed.  But, I'll proceed to try them now.

RoHe,

No go.  Followed steps exactly as provided.  When I turned the machine back on it prompted me to go to the setup utility.  Checked all of the settings, saved and proceeded to start Windows.

No change in BIOS, Win7 or CPU-Z.  16 GB in first two, 32 GB in CPU-Z.

Is this something new or has it always been this way?

Do you by chance have Nanya brand RAM in this system? Dell had issues with Nanya RAM compatibility a while back. If you have Nanya and the system is under warranty, contact Dell Tech Support and request replacement with some other brand.

And/or, if the other "identical" system has a different brand of RAM, try swapping it and see if this system will see all of that RAM, and now the other one only sees half.

Uncertain if this is "new" or always been there.

I recently pushed the system memory wise due to image processing and noted it.  Unclear if this had been the case since shipment.

Yes, I have Nanya brand RAM.  4 sticks of Nanya.

No, system is just over 1 year old - no longer under warranty.

The "identical" system does not have Nanya RAM.  It has 3 sticks of Micron RAM and 1 stick of Samsung RAM.

I'm at the point that I'll try to swap the RAM, but based on all that I've attempted so far I don't quite understand how that will make a difference.  I've rotated the 4 sticks of Nanya RAM through every slot  as well as only placing 2 sticks in at a time and rotating through and in all cases I get 16 GB recognized in BIOS and Win7.  If I have 4 sticks seated, the only difference is that CPU-Z shows 32 GB.  Based on this debugging, I would think this is telling me I have 4 good sticks of RAM with 4 good slots.  Am I missing something here?  I'm sure there may be something subtle that I may not be getting...

It's possible the Nanya RAM is defective and only allowing 16GB to be recognized by BIOS and the OS. CPU-z may see it, but doesn't mean it's working.

Disappointing that Dell mixed brands of RAM in the other system. Makes me wonder if you really have 2 matched pairs.

But either way, since you know all 32GB are recognized in that other system, if they're not recognized here, you probably have a motherboard failure. But I'm betting it's just crummy Nanya RAM. And in that case, you may want to toss all of it and buy 4 matched modules from somewhere like crucial.com.

Post back and let us know what happens when you swap the modules, but be sure to keep the 2 sets separate.

Looking over the cost of RAM.  Think I would prefer that this be a motherboard issue.  Cost me about half to replace the motherboard as opposed to buying 4 new sticks of RAM.

Regarding the matched pairs.  Based on all of the specs they are the same.  They were ordered for me and my office mate at the same time, identical systems.  Based on what I've been able to check with CPU-Z on each machine they appear to be the same with differences similar to the RAM discussion.  One other item I noticed was a different revision on the intel i7 chip between the two.

I'll try to do this swap and see what happens - easier said than done as the other machine, because it has the 32 GB working is being used often via remote desktop by other individuals to get work done.

And a question.  How could all of the Nanya RAM work as I've described but also have a defect that doesn't allow the BIOS to recognize when all 4 sticks are seated? I'm curious how this might be the case.

Could be an incompatibility in the RAM modules when both memory banks are filled, eg all 4 sticks installed. Or it could be a motherboard memory controller problem when both banks are filled...

But lets back up a nanosecond:

Do both systems have the same version of BIOS?

Do both systems have the same version of the Intel Chipset drivers?

Keep in mind that if you update BIOS, there's always a small chance it might fail and brick the motherboard. So be sure to read and follow the instructions closely, and disconnect all peripherials, except mouse, monitor and keyboard, while running a BIOS update.

Latest drivers for XPS 8500 are here.

Or just update the chipsets on the problem system to the latest version... You can use the chipsets from the Dell support page or go to the Intel site and let it scan the system and offer the latest available for the chipset in this system.

BIOS is up to A12, though I didn't see anything that fixes RAM issues listed in the versions after A09. I suppose you might consider updating BIOS on the problem system, in case the current flash is corrupted, but you do have the risk of bricking the motherboard to consider... And I'm not responsible if the flash fails...

Yes, both systems have the same version of the BIOS - A09

Not 100% certain that Intel Chipset drivers are the same - would need to check that.

BTW: if you search these forums, you'll see other XPS 8500 systems that only recognize half the installed NANYA RAM when 4 sticks are installed 

So I go back to my original comment about the RAM...And the fix is to throw the Nanya junk in the dumpster...

Too bad you didn't notice this while the warranty was still active and Dell would have swapped the RAM.

When you borrow the RAM from the other system, assuming the PC sees all of that RAM, test if it will see all of the installed RAM when half is the original Nanya and the other half came from the other system, keeping them as matched pairs in the slots. . If that works - BIG "IF" - you may only need to replace 2 of the Nanya sticks instead of all 4...

RoHe,

Much appreciate all of the suggestions.

May have an opportunity to try these suggestions out in the next day.

...and one more piece of information.

Placed the 4 Nanya sticks (originally from my machine) into the companion machine.

Result - BIOS, Win7, CPU-Z all recognizing 32 GB as it did with the original 4 sticks of RAM that were in the machine and are now in my machine.

So this is clearly NOT a RAM issue. And after taking the CPU out of the socket and inspecting, it doesn't appear that there is an issue there at least in what I can visually observe.

Any additional ideas - mobo, memory controller? Anyway I can do diagnostics on the motherboard?