I have an Alienware 17 R4 7820HK. It came with 16GB of DDR4 2666. I spoke with tech support because I had previously been told that it 32GB of DDR4 2666. I bought Corsair Vengeance 32GB DDR4 2666 model number CMSX32GBGX4M2A2666C18. It recognizes it as 32GB but as 2400. I chatted with a tech and he said it should work but it does not he suggest Hynix but Dell doesn't even have it. Does any 32GB DDR4 2666 work with the Alienware 17 R4? Is there a BIOS update that can be done to fix this?
Actually Crucial RAM is made by Micron and it is usually very compatible with Dell systems. And I am assuming that the 17 R4 does not have XMP settings in the BIOS? However the difference between 2400 and 2666 is very slight and most users would not see any noticeable change. The following video addresses that question well.
I have just upgrated RAM to 32GB 2666Mhz. But in AW 15 R3
Before 2 x 8 GB Micron 8ATF1G64HZ-2G6B1 (2666Mhz)
Now 2 x 16 GB Samsung M471A2K43CB1-CTD (2666Mhz)