[Regicide]

I am running a HP Laserjet IIIP PCL5 printer with cups. It seems to be running fine. But, it appears that because the printer is so old that it only has 1 megabyte of memory. Now, being cheap, I don't want to spend money on upgrading. So, there seems to be an error that when you print a page with a graphic on it, you must set the dpi to 150x150. Otherwise, it can be set at 300x300. So, my question is can I somehow make CUPS decide what kind of document it is being sent and change the dpi accordingly?
Also. when searching for the cause of the problem, I came accross this webpage: http://www.linuxprinting.org/show_pr...rJet_3P_w_PCL5.
I noticed on the 2nd comment, it hosts a driver for the printer. My second question is: could I load this driver into CUPS to fix the problem?