I have a 2013 iMac i5 2.7 Ghz 8 Gb 1600 Mhz DDR 3 Ram. I use mostly for batch processing large quantities of RAW files in Lightroom to produce jpegs. This causes big time delays in my workflow as well as building 1:1 and smart previews.
Costco have a deal coming up on the new 2017 iMac 27" Intel Core i5 3.8Ghz with 64Gb Ram for £800 less than the apple shop. I contacted them today and asked why they thought it was so cheap and they think that Costco will be installing third party RAM to get the price down. I told the techie my intended usage and asked did he think I would witness much increase in performance which he said would be massive (not convinced, but will carry on)
However, he thought my money would be better spent going for the 2017 iMac 27" Intel Core i7 4.2 Ghz with 16 Gb 2400 Mhz DDR 4 for the same price from the apple store.
I don't want to get into the windows mac debate here, but what are you views between the 2 machines of the same price for my intended use? Any help would be much appreciated.
Sorry forgot to add, my current 2013 iMac has 8 Gb Ram
So, a couple of issues here.
64GB Memory is great for many things, but doesn't really help Lightroom. Your speed in Lightroom really doesn't change going beyond 16GB of memory (except perhaps in rare instances like merging large number of large original files). So unless you are doing lots of other things on this computer (non-Lightroom), the 64GB is just a waste of money. (Side issue: usually the brand of your memory doesn't matter, it's the speed of your memory that would matter, but as I said, it doesn't really matter in LR, it does matter in other programs)
If you are experiencing slowness batch processing on your existing computer, the best thing you can do is get the fastest CPU you can afford. I would NOT recommend any i5 processors at this time, these are at least one generation old. You want an i7 or i9 or Ryzen chip for maximum speed, get the fastest you can afford. And because there is some sort of bug that slows Lightroom down (for some people) if you have more than 4 physical cores in your CPU, you want the fastest four-core i7 or i9 or Ryzen you can afford.