I have an Asus motherboard, H97-E, with G.SKILL's 2X4GB DDR3-1600 CL-9.
I wish to expand to 16GB, but find this excat type, is quite scarce nowadays. BUT a DDR3-1600, CL-11 can be found in stores near by.
Is it possible to combine CL-9, and CL-11 on same motherboard ?
Is my motherboard capable of running a CL-11 ( assuming mixing is not possible, and using only CL-11 )?
CL = Column Address Strobe Latency, which shows the number of clock cycles that pass from when an instruction is given for a particular column and the moment the data is available. In general, the lower the CAS latency the better within a given memory technology.
So, a CL-9 will be faster than a CL-11, all other things being equal.
Your motherboard's manual https://dlcdnets.asus.com/pub/ASUS/mb/LGA1150/H97M-E/E9092_H97M-E.pdf says not to mix memory modules with different latencies.
How much it slows down if you change to all CL-11 may not be noticed. A Tom's Hardware review showed a 2 % slowdown when CL-11 was tested vs CL-9, and that's before other hardware choices were factored in.
Since, with the 2014 design of your motherboard and its H97 chipset, at most you can run an Intel Core i7-5775C or i7-4790K CPU, so the difference won't be earthshaking, or even perceptible.
Is it possible to combine CL-9, and CL-11 on same motherboard ?
Yes; However, the highest latency module, will determine the latency for all modules installed in your system. This means all modules installed would have a CAS (Column Access Strobe) latency of CL-11. However, ASUS does not recommend you mix modules with different CAS latency, nor does ASUS explicitly indicate your motherboard supports that configuration.
Is my motherboard capable of running a module with a CAS latency of CL-11?
Memory compatibility with a motherboard is not determined by the CAS latency of the module typically.
Reference: CAS latency
K7AAY and Ramhound provided good answers.
Another thing to pay attention - the voltage.
You may check your current RAM voltage and buy new stick(s) that need the same voltage.
Otherwise, from my experience, You'll have problems.
I am using TwinMOS 2GB DDR3 which is CL-9 and 8GB TwinMOS CL-11 on my Asus H61M-K from the day windows 10 first pre-release. For me nothing seems wrong, but yes, they suggest choosing RAM with the same CAS latency for adaptability.
