I did some quick research (about 2 minutes) with my favorite Google search engine and found that the same cable works on both. If you have a socket that accepts the same connector, more than likely it should work.
Yes the cable works on many scanners. You will need appropriate software, which can be found at: http://www.butelsoftware.com/
I have heard that ScanCat Lite is not very good.
Thanks guys, I don't know why my 1st Google didn't turn up anything useful. I searched again after reading this and found it. Didn't know it was the same cable until now (and of course I missed it on the Wiki too!)
I just used the PSR-500 cable with a stereo-to-mono adapter on the end, into the PRO-84. Used the Load84 software from the PRO-84 Yahoo group - works great!