I’m building a small office server with a ROMED8-2T and single Epyc 7272.
The choices are: KSM32RD8/32MER or KSM32RS4/32MER. They are the same price.
A while back, someone made the mistake of asking, “what is the difference between X4 and X8 rank memory”. That received a long and technical answer, which while (probably) correct, is not really what people like me want to know.
What I want to know is, since Kingston says both will work in the board, and they are the same price, which one do I buy and put in? I assume either will work. But the fact that they make two models means that there must be a reason for one or the other.
What is the factor used to determine which one is needed?
The motherboard you are using has 8 memory slots, so I do not think it matters which one you use. With both being the same price I would buy the single rank version.
My reasoning is this - each rank is effectively seen as a separate dimm slot by the motherboard. With 8 dimm slots most motherboards have no trouble with the timings for accessing 16 ranks. But if you had a motherboard with 16 or more dimm slots, then getting the timings right for memory access across 32 ranks is trickier and can result in the motherboard running the memory at a lower clock rate to compensate. So you would definitely want the single rank memory for a board like that.
If I’m buying two sticks of 32GB to start with, would the dual rank have the same I/O as 4 16GB, where the I/O of two single rank 32GB sticks would be… the I/O of two single rank 32GB sticks?
In other words, would the dual rank allow more simultaneous memory throughput that would give a performance advantage over single rank, when not maxing out the board?