http://www.students.uiuc.edu/~bng/satmod/index2.html
below is the important bit of the page
Update: A correspondence of mine allowed me to help him install the 9.5 chip in his newer Saturn (actually, a very new model...manufactured in February of 1997). After opening up his Saturn, I found a small mini board attached in between the CD-R OM drive and the main PC-board. The board was labeled "PC-Trap". Apparently SEGA has added it's own little MOD chip, perhaps to confuse would-be MODders from MODding their Saturn to play HK and copied games. But from fumbling about trying to figure out what the #### this board actually accomplished, I failed to see its usefulness: When I removed the board, and directly connected the CD-ROM to the motherboard, I could still run games normally (original games, of course). So I tried replacing the board with the MOD chip and low and behold, the system worked normally, now booting-up HK and copied games! Then I also tried re-connecting the PC-trap board and the MOD chip together. When I placed the MOD chip in between the CD-ROM drive and the PC-trap bo ard, the system failed to recognize the HK CDs. When I placed it in between the PC-trap board and the motherboard, then it could read both originals and HKs! Very strange. So the moral to this story is that the PC-trap board serves no useful purpose bu t to discourage MODders into thinking that the MOD chip cannot be installed in the newer Saturns.
Another thing that I found out when I was installing this chip into his new Saturn, was that the 9.5 chip didn't need to be modded like I mentioned within this website (ie. The A, B and C jumpers need not be shorted like I had imagined). The MOD chip had already been shorted with the B and C points connected...the wrong configuration for the newer Saturns after August of 1996. But the chip still worked! Then I tried desoldering B and C and soldering together A and B (like it should be) and the chip stil l worked. So whatever solder ing these two points together means is also a mystery to me. But the only draw back with this chip is that you must have the CD drive door closed whenever you startup the system. If the drive door is not closed, then HK CDs cannot be read...it's like the chip was never installed. With the drive door closed at startup, it's possible to switch games as you like and the MOD chip works norm ally. Please keep this in mind if you are installing a 9.5 chip.
(Edited by megametalgreymon at 3:22 pm on Dec. 9, 2001)