Weird Polaris Cart With a Resistor?

[phaxda]

I have had this cart for quite some time and it does not work on my system. I just had it as a collection placeholder, but now that I have acquired a working version I was preparing to rid myself of this one. Cleaning it up I noticed that it has an opening at the bottom (unlike my working one) and I can see two resistors on the board. Why? Just curious. Here is a picture:

 

[Shawn]

Looks like an EPROM board inside there. Wanna sell that to me??

[Wickeycolumbus]

Strange, I will have to open up one of my solaris carts to see if it was like that. Is the outside the same as all the others?

 

Edit: just saw that it is polaris, not solaris. sorry

Edited March 25, 2009 by Wickeycolumbus

[phaxda]

Hmm, I just noticed that the front label is sliced clean in half; this cart casing has been opened before. Does not snap off easy--how does one get these open... I don't see a screw or anything, looks like it interlocks somehow in the middle. How odd! I'd like to not completely destroy the case, but it would be nice to see what is inside...

 

Also, yes, I am willing to sell it. All I get on my system is a black screen. PAL?

 

Yup, POlaris. The other one I have has a normal cart casing and you can't see inside to look at the chip. Label is the same, though.

[+batari]

Tigervision 3F bankswitching is unique in that it can be done with an EPROM and a single IC - a 74LS173. The '173 has tri-state outputs, so the resistors must be needed for when some outputs are in a high-impedance state.

 

Someone on the Stella list puzzled out part of how this chip does 3F, but did not consider how A12 is inverted.