What are processor Memory Limitations based on?

[bidmead]

This is a question I've put to memory vendors and never had a satisfactory answer. They just quote the official manufacturer's specs back at me. 

 

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I have an 8-bay QNAP TS-853 Pro, currently with 4GB of RAM and a Celeron J1900 processor. QNAP and Intel both spec the maximum memory capacity at 8GB.

 

However, it's my understanding that this maximum is derived from the number of memory banks available (2, in this case) and the maximum capacity of a compatible memory module at the time the processor was launched (2013), which was 4GB.

 

Would it be true to say that when  8GB DDR3 SODIMMs became available the maximum became 16GB?

 

I believe that 16GB DDR3 SODIMMs single modules are available too. Do you know if these would be compatible with this QNAP hardware (I'm not using QNAP's QTS operating system)?

 

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It's a specific question but I'd like to get to the fundamentals. What exactly is that max RAM spec based on? 

 

Is it the case that the number of processor address lines limits the number of banks? And that what limits the size of a bank is down to current manufacturing capability?

 

Anyone?

 

-- 

Chris