Hi there,
Sorry that some black square artifacts appear on your PSD's in Photoshop when zoomed in.
Which version of Photoshop are you using and what is your computer's OS?
Does the problem occurs while zooming into a particular PSD file or happens with all the documents?
If it happens with all PSD files, would you mind deselecting the option "Use Graphics Processor" located in Photoshop's Preferences > Performance menu, then relaunch Photoshop and let us know if it helps?
Thanks,
Akash