i have 4x8GB of crucial ballistix PC3200 memory.  I can say my system has been finicky with BIOS/AWCC updates and having to reset CMOS every once in a while (I do overlock my R10 via AWCC so that might also be a factor, if you don't overclock, you likely won't see issues).  At the very least, make sure the memory is all exactly the same (don't mix different brands/speeds).

In addition to Dell ram here is user validated 4x8 GB in Aurora R12 with model numbers.

for example Hynix HMA41GU7AFR8N-TF 4x8GB

the rams above are confirmed by users to work in Aurora R12.

The validated OEM memory is listed here: OEM validated memory 

Validated memory configurations are listed here: Validated Memory Configurations 

As you already found out, 4 x 8 is not a validated memory configuration. That's not to say that it will not work, just that it's not validated and therefore might not work.

These machines are somewhat finicky when it comes to memory support, so unless you are tech savvy and don't mind fiddling around with it, I would stick with the validated memory and configurations.

If you do have issues, Dell might not offer assistance for non validated configurations or memory, should it not work.

The corsair ram validated by user benchmark is Corsair CMH16GX4M2Z3200C16 4x8GB

they are Corsair Vengeance RGB Pro SL DDR4 3200 C16 1.35V Optimized for AMD Ryzen Black (CMH16GX4M2Z3200C16)

Thanks - I have an intel aurora not a Ryzen system. If mismatching brands is an issue that would mean discarding the ones it came with. Anyone know what brand (and product ID) is on the factory aurora r12 with intel?

Thanks for your help,

The HyperX from Dell will not work with the HyperX directly from Kingston.  The voltage and XMP profiles are different, as in one type works with XMP-1 and the other works with XMP-2.  You can not run two different profiles at the same time.  Someone is going to attempt this based on your post and end up with a non startup code and have to reset CMOS after removing the offending ram.  HyperX themselves will tell you not to mix modules.

Re: I have 2 8gb sticks of ram for my new aurora r12

your stock Dell ram likely have stickers that match one of these three samples (XW21KG-HYD, MIE, MIE2).

based on user benchmark there is evidence that at least the MIE2 and HYD can both run as 4x8 gb in R12.  So look for two additional ram that matches your stock ram (e.g., if you have MIE2, get another two MIE2).  You do not have to buy them directly from Dell. They are often available from third party seller on eBay etc. at discount price and of excellent condition, many of these were pulled from Dell Alienware.  Just make sure you check the seller picture (and contact seller for return policy in case you run into trouble).

xw21kg-mie2 (pulled from new PC)xw21kg-mie (Alienware R10)

You read it wrong, it's clearly written there not to mix.