Today I tried to use a DVI adapter from PNY on what I thought was just a normal DVI plug. However I quickly discovered that even though the flat pin and 24 other pins matched up there was 4 other pins surrounding the flat pin which prevented me from plugging it in. Just to make sure I check the back of a few PC's and see the 24 pins + 1 flat pin, with no four pins surrounding the flat pin. This is something I have not seen before and was quite confused, so I assumed it was done purposefully by PNY so you would have to use the adapter on their cards. Picture of the adapter below (sorry for quality it is just my cell phone).
I have tons of Nvidia 8400gs cards from: ASUS, MSI, EVGA, PNY, and Zotac we use them in just about every office PC and buy which ever ones Amazon has on sale on that given week/month/year. So I try and find another adapter, I come across a EVGA one, same deal the four pins are there again. So I check the Zotac and Asus which don't provide adapters so I'm left with the MSI one.... again same thing. So now the question shifts to what is the purpose of these four pins?
After checking a cable I have laying around (pictured below) I see this one has COMPLETELY different configuration! only 18 pins + 1 flat? It works fine, and displays full 1080p with 32 bit colors. So I don't understand if it works just fine with the 18 pins and one flat pin why do you need all 24? Also why do you need those additional 4 pins around the flat pin on the adapters?