Hello, Following your official advice on using SSDs as scratch disks where they are often boot drives can quickly lead to system crashes, and in my experience with Mac Pros, image corruption issues (lines of white added in color channels, garbled caches etc) when the system runs out of space. Not to mention it slows the system down to a halt where one cannot even save the file to deal with the issue.
Why not set a 'use as scratch disk until X GB left option on each scratch disk so that we can avoid this issue altogether. Especially since most SSDs perform worse as they near full capacity and that most use boot drives that can easily be filled by photoshop, this sounds like a simple but effective method of adjusting photoshop for contemporary systems. (I have 32GB Ram and 100GB free space on my SSD and PS still manages to fill it even when I limit history states)
Thank you for the input regarding scratch disks. This idea has been implemented into Photoshop 20.0, which is available for download today. Please open the Creative Cloud app, download the update and let us know how it goes for you. If you do not see the update immediately, sign in and sign out of the Creative Cloud.