does it hve to be the same

Solution
Best bet is a single packaged set of DRAM, mixing any packages or sticks can be problematic, sets are packaged both as being tested to work together, and if planning to use XMP, they are programmed for the specific number of sticks in the package, i.e. a 2 pack of stiks may need a tRFC of 208 while a 4 sticks package may need the advanced timing tRFC up around 314
It is recommended the RAM specs be the same (voltage, CAS latency, ECC/Non-ECC, etc.). Mismatched RAM can cause problems such as random shutdowns and other problems.

"NON-ECC/Non-parity — Most desktop and laptop computers take NON-ECC or Non-parity memory.
ECC/Parity — ECC or parity modules look for errors in data and are most often found in servers and other mission-critical applications used by large networks and businesses.
Unbuffered — Most PCs and workstations use unbuffered memory which is faster than registered memory.
Registered/Buffered — Registered or buffered modules delay all information transferred to the module by one clock cycle. This type of memory is primarily used in servers.
Fully buffered — Designed for next-generation servers, features an advanced memory buffer.
CL — CAS (column address strobe) latency, which is the number of clock cycles it takes before data starts to flow after a command is received. Lower CL is faster. Modules with different CL can be mixed on a system, but the system will only run at the highest (slowest) CL.
Component configuration — (For example: 64Meg x 64) Indicates the size of the memory chip components on the module.
Voltage — For example 2.6V. Indicates the power used by the module. The lower the better.
Check the glossary and FAQs for more detailed definitions. "
The above was from crucial.com
 

Tradesman1

Legenda in Aeternum
Best bet is a single packaged set of DRAM, mixing any packages or sticks can be problematic, sets are packaged both as being tested to work together, and if planning to use XMP, they are programmed for the specific number of sticks in the package, i.e. a 2 pack of stiks may need a tRFC of 208 while a 4 sticks package may need the advanced timing tRFC up around 314
 
Solution