I did some experimenting with single rank v. dual rank memory in Time Spy and thought I would share my results here.
10900k at 5.3 core/4.7 ring
Single rank kit- Team Group 8-pack 4500cl18 xtreems
Dual rank kit- G. Skill Trident Z 32gb 3200 cl14
I used Time Spy cpu run only to compare results, and used the cpu score to measure gain in performance for each timing. I used maxmem to reduce the 16gb down to 5gb, and from 32gb to 10.4gb. For memory timings I used flat primaries with tRAS=tCL+rRCD(RD)+2, tWL= CL-2, tRDRD_dg and tWRWR_dg at 4, maximus tweak mode 2, and used 1t for all of the single rank timings, but for dual rank 1t only worked on the first test, and 2t was used at the rest of the timings. Everything else on the memory was kept at auto, I have attached Asrock Timing Configurator screenshots so you can see the other timings that were trained for each freq. Here are some screenshots from both single and dual rank kits showing the auto timings that were trained: https://imgur.com/a/hYNo2qC
I used only as much voltage as necessary to complete a run and did not play with increasing voltage for additional stability or to see how it impacted a score. For this testing I only used a limited range of frequencies based on the limitations of the kits themselves, would be interesting to see if it keeps scaling linearly. With these limitations lets take a look at the numbers:
16gb Single Rank
32gb dual rank
How much faster is Dual Rank?
As you can see dual rank is slightly faster at jedec speeds (I didnt look at jedec timings to make sure they were the same, but how close those scores are seems to indicate they are the same), but it surprised me at just how much faster the dual rank kits are once they get up to 4000cl15.
Some of this may be obvious to the more experience benchers, and looking at the world records they use a large amount of memory, but I thought it was interesting to have actual numbers to see just how much better the dual rank is. I would love to see someone with a quad or higher channel setup and see how their numbers scale with these.