Originally posted by MadMathMind Fast RAM isn't going to make a huge difference for still images. The amount matters a lot more. Fast RAM is needed in applications where bursts of bandwidth are needed--games are the big one. Keep in mind that enterprise-class workstations use ECC RAM, usually at speeds significantly slower than the fastest RAM available. The ECC itself slows it down a lot as well. In the end, there's no real performance loss because even the bandwidth that the slower ECC RAM provides is overkill.
i've been overclocking computers for many years, and everything that i've seen agrees with that... fast ram is big $$$ and any speed improvements that you see will be very small, and they will depend on a number of factors.
"...we would actually say that Photoshop CC shows little, if any, performance difference with ECC or Registered ECC memory despite what the total benchmark results indicate."
Debunking a Myth: DDR3 RAM vs. ECC Memory Performance - TechSpot
if ecc vs. standard ram doesn't make a difference, fast ram won't either... when it comes to photo editing, you'd be much better off spending your money elsewhere.
spending more money on multiple cpu cores vs. spending more money on a faster gpu is the other big question... both amd and nvidia take advantage of opengl these days.
photoshop vs. lightroom vs. premiere pro vs. whatever can all take advantage of multiple cpu cores, but they don't all benefit to the same degree... here it is from 2012, but things have changed:
https://forums.adobe.com/message/4289204
you have to look at your workflow; edit jpeg vs. edit raw, lightroom or no lightroom, lightroom vs. dxo for raw processing, etc.