David Os

So guys, i just upgraded my iMac RAM in the following way: 2 (pre-installed) Elpida DIMM's 4gb + 2 (new) Crucial 8gb DIMM's for a total of 24 Gb with all the compatibility specs i could find (Haven't done any benchmarks) [First Image Below]. And its working like a charm, i can now have 5 plus apps opened including LR and PS and switch between them (which is what i wanted) memory pressure in activity monitor is on the floor compared to old 8 gb being always to high with just Lightroom and Photoshop opened, i see workload in PS is not stealing so much from de Hard Drive, files take the same time to save but that's because this is the same ol' 7200RPM HDD but ill be fine with that. Closing multiple programs now is too much faster and that was the most annoying thing happening to me before upgrading.

I assigned 45% of memory to Photoshop, increased Cache levels to 8 and history states to 75 as i do a lot of brushing to my retouching, no problemo working with the 46 mp files even at 4.5 gb file size (with a couple of layers tho)

Now, why the system is not giving me problems if the new kit of RAM Memory is so different from the preinstalled one, considering this as a 6+ years old machine? i thought there would be a problem, is it becasue OSX (El Crapitan) is optimizing in some way? Is it because it's DDR3 and such low Frecuency dont stress the Processor with such slot population? Is it because it's Intel platform?
 
I bought 16Gb kit (2x8) CAS18 3200Mhz (idk single or dual rank tho9 [Details in the second image below] for my new (under construction) PC Rig and it will be a Ryzen Third generation system (But lets assume i buy a Motherboard for 2nd gen Ryzen (lets say Asus Crosshair VII Hero X470 - one of the best in its category, and lets say i buy a R7 2700x just for the sake of realism as Ryzen 3000 isn't launched yet)... Do you think there'll be a problem if i jut buy the same kit of 2x8 as before, populate the 4 slots of RAM and works just as fine as this? i am totally aware i'm working Dual-Channel here.

Thanks, @ch3w2oy, @Bearmann, @badreg, @Origami Cactus, @Brink2Three, @GrockleTD