Upgrading ram but don't know what to choose

I want to upgrade the ram of my P650RE3 (NP8657) and I want to buy the same ram i have but there's only one seller of the same ram and it doesn't look like a trustworthy seller so I'm wondering what ram should I buy?

Samsung RAM: http://www.amazon.com/Samsung-DDR4-...d=1454551945&sr=1-1&keywords=M471A1G43DB0-CPB

If i bought that ram, I'd be able to utilize the dual channel but what if I just bought another 2x8gb + my existing 8gb, will the dual channel still work?

 

You can mismatch RAM sticks and yes, dual channel will still work. Assuming you have 4 SODIMM sockets, just populate the sockets corresponding to one channel with a matching pair and the other with the other matching pair. It should be clearly mentioned in your manual which goes with which.

 

Can I not make my computer use the 2x8gb ram that uses dual channel and use the other 8gb ram as a "last resort" so dual channel would work unless I need to use the 16gb++ memory

 

Is your 8 GB currently installed a single SODIMM? Anyways, any remotely recent Intel CPU and AMD CPU will run unequal amounts of SODIMMs in what is called asynchronous dual channel mode. You can look it up, but the short and long of it is that yes whatever your CPU can operate in dual channel will run in dual channel mode.

I figured your SODIMM configuration was 2x4 GB and that you'd end up with 2x4 GB + 2x8 GB, assuming you have 4 SODIMM sockets.

 

I actually have 1x8gb 2133mhz installed. Also, I'm running my laptop on discrete mode so my Intel CPU isn't functioning.

 

Then, just put your 2x8 GB kit in the other sockets and it'll run in dual channel mode until you hit > 16 GB RAM used. The last 8 GB will run in single channel mode.

 

Would it run on 2500mhz or would it clock down to 2133mhz when it reaches >16gb?

 

It will run at 2133 MHz 100% of the time, RAM will always run at the slowest common denominator.

 

How would I know the RAM I'll be purchasing is compatible with my laptop?

 

Does your laptop take DDR4 or DDR3? Is it ECC or non ECC? Those are the two questions you have to ask yourself. If you need non ECC DDR4, then any non ECC DDR4 SODIMMs will do. The will run at whatever speed the rest of your system can handle. RAM is never set to run at a single frequency. They have a table of frequencies they can run at and it's usually whatever is supported by the DDR version of your RAM. That means that DDR4 SODIMMs rates at 2500 MHz also is also capable of running at 2133 MHz without any issues.

 

All I know about my existing ram (Its module part number is M471A1G43DB0-CPB) is that it is DDR4 and has 260 pins.

 

Just get DDR4 260 pin RAM then. Try to match speeds or get faster.