The RAM requirement is not by the CPU but the tasks that you need CPU to do. In simple if you have a programs that does millions of calculations for that it need to keep large amount of unprocessed information in the RAM. Your case is about the same. I supposes the information going out and in the RAM uses up all the RAM which eventually asks windows to utilize the shared memory(which performs slower).

on normal use PC uses 1.7-2.5 GB Ram depending on number of applications open.

lets say 7.9(available MEM) - 2Gb(Normally used MEM) =5.9

you are left with only 5.9 Gb for the remaining programs (your Calculations)

It seems that by your method all the memory is exhausted along with shared 5 Gb. the best call for you is to double the RAM. which will be able to keep enough information till it is processed.

these might help you.

http://superuser.com/questions/78362/what-is-the-relationship-between-cpu-usage-and-ram

http://stackoverflow.com/questions/17017593/why-cpu-instruction-executed-in-ram

http://homepage.cs.uri.edu/book/cpu_memory/cpu_memory.htm

hope it helps.

Thanks.

The RAM requirement is not by the CPU but the tasks that you need CPU to do. In simple if you have a programs that does millions of calculations for that it need to keep large amount of unprocessed information in the RAM. Your case is about the same. I supposes the information going out and in the RAM uses up all the RAM which eventually asks windows to utilize the shared memory(which performs slower).

on normal use PC uses 1.7-2.5 GB Ram depending on number of applications open.

lets say 7.9(available MEM) - 2Gb(Normally used MEM) =5.9

you are left with only 5.9 Gb for the remaining programs (your Calculations)

It seems that by your method all the memory is exhausted along with shared 5 Gb. the best call for you is to double the RAM. which will be able to keep enough information till it is processed.

these might help you.

http://superuser.com/questions/78362/what-is-the-relationship-between-cpu-usage-and-ram

http://stackoverflow.com/questions/17017593/why-cpu-instruction-executed-in-ram

http://homepage.cs.uri.edu/book/cpu_memory/cpu_memory.htm

hope it helps.

Thanks.

Dear Abdul Wahhab, Thanks a lot for your helpful answer.

As he said minimum amount of RAM is not chosen by CPU type. 

Two important factors that will decide the minimum size of needed RAM and maximum possible RAM are your operating system/target applications and Chip set of your mother board.  

Since all of the chipsets regardless of the motherboard brand are fabricated by intel you can compare them in intel website

http://www.intel.com/content/www/us/en/chipsets/performance-chipsets/chipsets.html

However, most of the normal chipsets supports up to 32GB of RAM. 

regarding minimum RAM size supported by fdifferent operating systems you can find it also in their website for example the following links shows the minimum required RAM for Windows 7.

http://windows.microsoft.com/en-us/windows7/products/system-requirements

By the way this is the minimum but if you are looking for faster processing time you may need to add as memory as possible to your PC. 

At the end if you are interested in assembling a normal PC 8-16 GB is enough for you. In summary based on your need first you need to choose your chipset and then look for suitable mainboard with that chipset and then choose your CPU which matches the CPU socket of your mainboard. One of the famous weblogs for assembling computers is http://www.tomshardware.com/. 

Good luck :)

Thank you Ashkan.