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No offense taken, here is why...
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- Jason
I built my system back in 2010 and have been using the x58 Asus Rampage MOBO ever since
I have only done a GPU upgrade from SLI to Tri-SLI since then and that was back in 2013.
Ok, just did some online digging and now I remember back in 2013 when deciding to go from two GPU's at x16/x16 my MOBO could do three but only at x16/x8/x8 and I was concerned so after looking into this I discovered/remembered exactly what you are saying, that the performance hit for this change was not something to be worried about. But, I'm not sure about x8/x8 having the primary GPU at only x8 ... IDK, never even looked into if that would be an issue.
As far as my opinion about the benefit of multi-GPU is concerned. For me anyway, I created an MS Excel spreadsheet just before installing the new GPUs and the worksheet was pretty comprehensive. It included a list of various benchmarks like in-game (pre-cooked) ones like Metro/RE/TomeRaider/SleepingDogs/BioShock/Batman/.../...etc and then Synth-Benches like Furmark, Fluidmark, Tessmark, 3Dmark's, Cinebench, Catzilla, Unigine ..etc. The spreadsheet has multiple tabs for eg. (old-GPUx1, old-GPUx2, old-GPUx3, new-GPUx1, new-GPUx2, new-GPUx3, GPUx1--Compare-old/new, GPU-SLI--Compare-old/new, GPUxTRI-SLI--Compare-old/new). All that was needed was to run the benchmark of choice and input the FPS or Score. Then, results generated for Min/Max/Avg for each group/type of benchmarks. This allowed me to draw an accurate comparison of benefits gained from 1/2/3 GPU's and also the benefit gained from new generation GPUs comparing 1/2/3 with the older and seeing if SLI is still being a valid scaling benefit. Also, to note was that I realized that even though a percentage sound good like 35% boost adding 3rd GPU, unless the system is already pushing the difficult stuff FPS over 30 then the increase even at that percentage is not that beneficial. The spreadsheet presents the information in bar-graphs, Avg. FPS Delta, and Percentages Scaling Increase.
I even named it "Bench iT 123".
What I found was that there was a good performance increase when using SLI The average between both game engine and utility synth benches was (80%), and a smaller performance increase on top of that when doing Tri-SLI (35%). Since I knew an investment in GPU's along with Waterblocks and Backplates are made with considering the future in mind, and also that by the time I may see a GPU fail my GPU model may no longer be sold it made perfect sense (to me) to get three GPU's with one being a possible spare to still allow for SLI in the advent that one went bad.
Memory Channels....well for gaming, ummm, I guess, well, probably wrong about that. Remember the last time I begin my build was in 2010 and they were marketing Triple-Channel memory
Unfortunately for me, when 2017 comes around and I go to build my next system. I am sure to get whatever is at the top whether multi-channel or multi-gpu. I just couldn't do it any different.