Does more system RAM (like 128GB) matter when working with complex high resolution files?

My last system had 64GB and never came close to using it with Photoshop, so I saw no reason to put more rRAM in my current system.  I've got two small files open in Photoshop at the moment, and I have restarted it a couple of times today.  This is what I am seeing in my primary scratch drive.  That's 60GB of data that Photoshop is reading and writing to, so Like @D Fosse  said, the speed of your scratch drives is crucial.

10 to 15 years ago an HDD might do 100 to 120MB/S.

I knew that m.2 drives were managing 10kMB/S, but I just found this.  That's > a hundred times faster!  

I often work with very large resolution files. Think photos from an 61MP camera, often multiples of these stitched, and then also with several smart layers of edits. PSB files up to 4-5 GB sometimes. And I want to build a somewhat future-proof system, so the file sizes might even increase… would 256GB ram be better than 128GB, for example? I currently have 64GB in my system and it seems like sometimes it's a limiting factor. Photoshop gets really slow, starts buffering (I suspect) etc. I want to mention I use intensive plugins like NIK and Topaz, so this could also be a CPU limitation perhaps.

By @loco27057486xady

If you’re editing 4–5GB documents then it’s reasonable to consider 128GB RAM or more. But yes, there is a point of diminishing returns, and the cause of a slowdown is not always obvious. So to spend the right amount of money in the right place, try to analyze for bottlenecks using Task Manager. When Photoshop is getting slow, open Task Manager and look through the sections. Look through CPU, GPU, memory, storage… See which system resources are operating at their limits, and which are not, so that you are putting your money in the right place.

CPU. Photoshop typically won’t use all CPU cores constantly like a video editor, because it’s editing only one frame. Some features can max out the CPU, but only for short periods. So the CPU is usually not the problem unless the computer is old, where the CPU has relatively slow single-core performance compared to today.

GPU. Photoshop might not tax the GPU for most operations, but specific features are very dependent on GPU performance, and could resuyt in a bottleneck with a weaker GPU. Some of the features that depend the most on GPU performance are the newer ones that use machine learning/AI.

Storage. If you’re using SSDs they’re faster than Photoshop needs most of the time, for basic I/O. But storage performance is actually more critical for memory usage, see below…

Memory. What does the Memory graph look like in Task Manager? Is it always filled, or usually not filled? If it’s always filled then more RAM could be a good idea. If it’s not typically filled then the bottleneck is somewhere else, and buying more RAM may not make any difference.

For Photoshop, memory usage is really about its Scratch Disk feature, with RAM being a sort of fast cache for that. Because of that, the Scratch Disk(s) assigned in Photoshop preferences should be both as fast as possible and as large as possible. A slowdown could be caused by a scratch disk being too slow (like on a hard disk drive instead of a solid state drive), or too small (so that the volume runs out of free space).

Also, in Photoshop, check the Efficiency indicator in the Status Bar. The Adobe Help article “Optimize Photoshop Performance” says…

If the value in the indicator is below 100%, Photoshop has used all available RAM and is using the scratch disk, which slows performance. If the efficiency is less than 90%, allocate more RAM to Photoshop in Performance preferences. Or, add more RAM to your system.

(If any Mac users are reading this, you can do the same analysis; the Mac equivalent of Windows Task Manager is macOS Activity Monitor.)

Thanks everyone for the replies. The information about scratch disks is very interesting, I never gave that too much thought. Seems I have to look more into this. 🙂

I have 256GB RAM here and I've never seen Photoshop use it (I installed it for physics simulations in 3D applications not for Photoshop). As D Fosse states above, the scratch disk is used no matter what RAM you have and a large space on a fast M2 NVMe drive will be the most benefit with large files.
Dave

@loco27057486xady more RAM and GPU is always a benefit and not meaningless. This has a direct impact on processing speed. If you are working with files as large as you state - I would be maxing out RAM and GPU now.