How much do you think two sticks of RAM vs a single stick of RAM affect the speed of these work units assuming all other variables are the same e.g. GPU, CPU, clock speed.

I would imagine considerably.

I see no immediate reason why two modules would slow down the performance, as a second module does not necessarily change the access time or timing. One thing which could reduce the access time is bus multiplexing due to a large memory size and therefore increased address range. That said, it is a matter of total RAM size but not dependent on the particular configuration (e.g. either using 2x8G or 1x16G modules). Another thing is an eventual signal interference on the bus having all banks used, which may require a slightly slower timing. But again, that normally is not the case with two banks.
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I would love to see HCF1 protein folding and interaction simulations to help my little boy... someday.

I was thinking one stick of RAM would be considerably slower than two due to the single channel he would have with one stick.

I was thinking one stick of RAM would be considerably slower than two due to the single channel he would have with one stick.