Ram upgrade issue for Zbook15

[Linux588]

Hi I asked this question before and was told to  buy

Crucial 4GB Single DDR3/DDR3L 1600 MT/s (PC3-12800) Unbuffered SODIMM 204-Pin Memory - CT51264BF160BJ

Which was matched for my Zbook Workstation laptop serial

[Personal Information Removed] SKU F7N24UP#ABA Version A3009CD10002.

I bought the 4 gig stick and on the back of the laptop you remove the

plate and it has 2 slots to install RAM. The original RAM is 2 slots or

dual stick setup at 4gigs each on the motherboard I believe, its Samsung

RAM giving a total of 8 gigs. I wanted to upgrade to 12GB  by adding this

one that is recommended for this model yet the bios never sees the extra

RAM. I even tried 2 other 4 gig RAM models lying around to see if I can get

16. So far I tried the memory scan check in bios, I removed the cmos battery

for 10 mins, I reset bios to factory defaults and it refuses

to add the RAM. Any idea whats wrong with this laptop ?

[banhien]

@Linux588 

You can use DDR3 OR DDR3L but won't mix because they use different voltages.

Regards.