I have this problem since version 22.4 then 22.4.1 and now version 22.4.2 of Ps, too!
I have post a feedback at feedback hub but no solution offered!
Why full amount of RAM does not recognized by Ps from since version 22?!
OS: Win 10 x64, 12 GB RAM
Ps recognizes full RAM in SysInfo but not in Preferences (SS below):
It's not just you. v21 on my Mac has 1 GB more memory available than v22, all settings equal.
I had no problem till v22 update! What does mean "Advance"!!! Full amount of RAM is recognized by Ps but it can't regognize in "Preferneces". I think it's something about rubish "Neural Filters", though most of them (NFs) are server side processing!
It does not sense, the "Advance"! I don't need more RAM (more than 12 GB). Why I should spend money for a software bug!
What is running on your system? From what you posted I see in you Photoshop system information that Photoshop see your system has 12GB of RAM and there was 10GB of RAM free when photoshop was started. That after Photoshop started and you edited your Preferences the Free RAM was down to 8GB. Photoshop is currently using 2GB of RAM. The numbers seem to be reasonable to me.
I see Photoshop Also uses 2GB of Ram on my system.
I have no new installation (no new software or app is installed on my PC) and I have full scanned the whole drives.
Since v22 this problem starts to appear! I am wondering too(!) how Ps can see full RAM in SysPref but can't see in Preferences!!! (since v22 till latest v22.4.2). I didn't change anything on my system, Ps has changed its behavior since v22! Version 22.1 has such a rubbish problem with my dedicated AMD graphic card!
You can check my System Spec and Task Manager and Page File settings (set to automatic mode, as always Win 10 manages Page File).
The amount of Available RAN changes with use. Starting Photoshop your system info shows the Photoshop see your system has 12GB of RAM and the currently there are 10.2GB of RAM free available. By the time you can edit you Photoshop Preferences Photoshop has consumed 2GB of RAM available RAM is down to 8.7GB and you set the Photoshop can use 100% of free RAM if it want to.
It's being discussed here:https://feedback.photoshop.com/conversations/photoshop/photoshop-224-does-not-recognize-full-memory-...
You can go sign in there and add your voice. The feedback forum is where the Adobe Product managers are.