My system specs are Windows 10 Pro 64, Intel i7 6600k overclocked to 4.2ghz, 32gb DDR4 ram, Nvidia GTX960 GPU. I keep Lightroom installed on one 256gb SSD, I keep catalogs on another 256gbSSD, and the raws on a third 500gb SSD while editing. Even so, Lightroom seems blindingly slow in the develop module. If I'm not using any brushes or spot removal, it's tolerable, only maybe a second of lag. But any brushing or spot removal, forget it. The amount of time I waste editing while waiting for the program to catch up is obnoxious, especially when I have 1,200 pictures to edit in just one wedding. Nothing wrong with the file system or software, I have an exact duplicate system with the same specs that my partner edits on and it's equally as slow.
So what hardware can I upgrade to make Lightroom snappier in the develop module? I don't think going to 64gb ram from 32gb will help since LR is not using more than 7gb max at any time any way. Everything I've read online says graphics card doesn't matter as long as it has at least 2gb GPU ram, which mine does, so no point in getting one with 8gb of GPU ram. The only thing I'm left with is processor, but my 6600k processor is already over clocked to 4.2ghz so the only benefit of upgrading would be to have 8 threads instead of 4. Will those 4 extra threads do anything for the develop module?
Any other ideas?
Check the settings in the Preferences dialog, Performance tab. If you have the GPU optimization turned on, see if turning it off helps any.