I use CS6 on a Mac pro os 10.8.3 & print to an Epson Pro 4900.
If I print an image via LR4 print module the print comes out at 12 X18 in. Recently I have tried that same image via CS6 and the print comes out at 6 5/8 X 8 1/2 in.
In Print Settings in Printer Setup in the print module of CS6 stats "Super A3 / B 13 X 19 but the printed image dimensions are a little over half of that.
The printer used to print normally in CS6 print file.
What's the image size in Photoshop's Image - Image Size dialog?
Does the image fill the page properly in the Photoshop print dialog preview area?
Maybe it would be good for you to post a screenshot of what your'e seeing in the print dialog.
I tried your suggestions without success.
I went back and tried adjusting the "Scale:" percentage in "Scaled Print Size"
The image size in the Image Dialogue box is 11 X 16.5 in.
In the Print Dialogue Window the following info is:
I then printed out the image after adjusting the Scale percentage which yielded the following results:
It appears to me that CS6 is applying an upper size limit but I don't have any idea why.