Friday, September 2, 2016

Carts, carts, carts...

Might have gone a little overboard here, but maybe that's good. I tried some new things and they worked out...
First off I went back and made a label for the Thunder Force III Multicart I made a while back. This was my labor of love to the series - full of patches to unlock everything I wanted from the series. ;) It was my first cartridge PCB from scratch, and it worked okay. I still have a few to get rid of though...
After that, a guy online followed my guide and created a Shinobi cart. He did a great job on the menu, and gave me a copy to help finish it. He wanted to use 4MB EPROMs instead of 2MB, so I modified the board for him. It still takes 2, but the whole multicart fits in just one now, so it's a bit cheaper to build, too.
But, after building that test cart, I saw a few things that still were not quite perfect, like the top left IC still bumping the posts inside the cart... so I tweaked that up. And while tweaking it up, I got to thinking that the one other series I wanted to do was Ecco the Dolphin. The only issue with Ecco... two of the games are 1MB, like my cart supports, but one of them is 2MB.
After some thought, I think I came up with a design that puts the second game on the second chip, so it can have the larger range, while keeping the first two on the first chip. Because I'm dumb, I decided to use 2MB chips. ;) (But, I used my last one, so one is a 4MB chip doubled up anyway). I went ahead and modified the PCB, but, I didn't order any at the moment. I just used jumpers for the build...
That's still burning, which is why I'm not in bed yet! Almost. ;) But the new layout lets me jumper for 2MB or 4MB chips (although Ebay suggests there's no reason to get 2MB anymore)... it also lets me jumper the second chip for 1MB or 2MB banks, so my Ecco cart works more easily. ;)
Ecco was a software challenge too, though. Since I needed to fit two 1MB games in the first 2MB chip, I had to figure out the menu software. Turns out Ecco 1 has about 34k of unused space at the end of the cart. A little compression wasn't quite enough to get my 44k menu down, but stripping out a lot of the unused BASIC runtime was. ;)
Finally... earlier this week I put together a Jaguar cartridge PCB. It was the first time I did a shape, and the first task for my new calipers. ;) I made a few small mistakes, but nothing too critical, and it seems to work fine. Games normally run 32-bits wide on the Jaguar, but changing the header lets most run at 16 bits (as we learned on the Skunkboard). For my test cartridge I forgot to increase the configured bus speed to make up for the narrower width, but that didn't seem to impact it anyway. I have some sockets coming to make testing easier.
Anyway, I really disliked the original layout, and since I needed to fix it anyway, I redrew the lines a little more curvy, cause curvy PCBs are rare and fun. I also added the missing save EEPROM, since it turns out those are not too hard to get after all. This cart also jumpers for 2MB or 4MB, but since that's the size of a single Jaguar game I never intended multicart on this one. Just cheap single carts. ;)
Parts are funny... people sell empty Jag shells for $3 to $4 each. But for the Genesis, just grab entire boxes of sports titles for 25 cents a pop (as a bonus, a lot of sports games have 32k RAM chips I can put into my TIs. ;) ).
Well... picture layout isn't very good here, but at least it's easy. Looks like the burn is done, let me go finish that cart and see what happens.

1 comment:

  1. Well, damn, it didn't work. Ecco 1 worked, but it's in the same bank as the menu. But the fact that Ecco Jr, on the same chip, also failed, gives me some hope I'll be able to troubleshoot it. After sleep. ;)