Earlier quoted context omitted.
Could be the disk speed.
No disk drive. Running off of an ADATA Premier SP600 256 gig SSD, which is supposed to have 540MB/s read, 290MB/s write.
I have CS running on and old i3 machine with 8 GB of RAM with an SSD and an integrated video card, and Photoshop runs as fast as in my MBPr i7.