I'm heavy into optimization for my job and I'm trying to better understand how to select RAM quantities. From my reading:
For the same DDR4 memory speed and DIMM type, more ranks will typically increase the loaded latency. While more ranks on the channel give the memory controller a greater capability to parallelize the processing of memory requests and reduce the size of request queues, it also requires the controller to issue more refresh commands. The benefits of greater parallelizing outweighs the penalty of the additional refresh cycles up to four ranks. The net result is a slight reduction in loaded latencies for two to four ranks on a channel. With more than four ranks on a channel there is a slight increase in loaded latency.Quote source: Useful to get the definition of "rank".
Subsequently, if I want to reduce load latency, I would think I want two to four ranks on my RAM. However, how do you know how many ranks something is?
For example, if I purchase 32GB RDIMMs, how do I tell how many ranks that RAM has?
Update: For anyone else who has to do this: I went into my company's part lookup tool and was able to pull the info. That got me this string: "DIMM,32GB;2933,2RX4,8G,DDR4,R". This post is helpful for understanding that output. The 2RX4 means 2 ranks of 4, each 8GB in size. If you're just looking it up commercially, you should be able to search by the part number if you're using Newegg or something.