You could try out this PS action - might work.
If you know how many you need to chop it up by...
View > Show Grid ( or Ctrl+' ) use your rulers and guildlines then
Edit> Preferences > Grid and place your Gridline and Subdivisions to your needs (might want to check your line colours will be visible over your work)
If you set up your grid line correctly, you could now use the rectangular Marquee Tool to drag select to each section.
Cut and paste into a new document, or use the crop tool to snap on the grid and, if necessary flatten the document, save as something else and then using your history, return back above the crop and start again to the next part.
If you want guidelines / rulers - or the grid is getting in the way...
View > Rulers ( Ctrl+R ) > move your mouse to the ruler, the mouse icon will change. > Click drag and guide from the ruler to your grid and snap it into place.
Continue using both top and side rulers to set guides along your division lines > View > Show > Grid to hide the grid ( or Ctrl+' )
You can then crop/marquee snap to your guidelines without the grid.
hope it helps.