2048K Cartridge Board

[+Ksarul]

I've been having a lot of fun with ExpressPCB this weekend. I've been mulling over a cartridge board that would allow more than 512K for a while now, and I think I have all of the potential hardware problems identified and resolved. I went back to square one on the cartridge boards and eliminated the entire jumper farm as the first step towards doing an updated board, as I initially expected 512K to be the low end for this board's possible EPROM sizes--an assumption that was wrong, as I have been eble to extend the low end to 128K EPROMS (certain 40-pin types). The first step was to add a pair of additional latches, which was done by replacing the 74LS378 with a 74LS377. The elimination of the old jumper farm allowed me to place it in the same relative position as the 378--and the cartridge case will still close nicely with it in place.

 

The next problem was getting a 42-pin EPROM in there. The M27C160 was the basic chip I wanted to shoehorn into this thing, as it will operate as a 2MBx8 EPROM (or as a 1MBx16, which we don't want here). Some careful trace arrangements allowed me to put it into the same general area as the old 32-pin socket--again with no impact on the ability of the cartridge case to close. Now came the fun part. The 1Mx8 chip uses the same pinout as the 2Mx8 chip, but the weird things with these chips is that the most significant address bit is always on pin 30. Time to build a new jumper farm. Now I have two jumpers, one for each of the 42-pin chips used.

 

Some more research indicated that there is a series of 40-pin chips that uses an identical pin-out scheme, so long as one ignores pins 1 and 42 of the larger chips. I could now support smaller chips with very little change to the layout while doing it. The smaller chips are available in 512K, 256K, and 128K sizes, and the ability to support them adds just three more jumpers. Now I have a 128K to 2MB board, ready for all kinds of programming goodness.

 

Assuming the menu is extensible to this level, this would allow us to put all four of Gazoo's game cartridges onto a single cartridge.

 

The layout is complete, but I still have to go over it to validate each and every connection to make sure I didn't miss anything. I'll probably do a test run of them in a month or two. . .maybe in time for Chicago.

[+InsaneMultitasker]

 

Assuming the menu is extensible to this level, this would allow us to put all four of Gazoo's game cartridges onto a single cartridge.

Just wait - we haven't seen Gazoo double stack this board yet.

[Gazoo]

I've been having a lot of fun with ExpressPCB this weekend. I've been mulling over a cartridge board that would allow more than 512K for a while now, and I think I have all of the potential hardware problems identified and resolved. I went back to square one on the cartridge boards and eliminated the entire jumper farm as the first step towards doing an updated board, as I initially expected 512K to be the low end for this board's possible EPROM sizes--an assumption that was wrong, as I have been eble to extend the low end to 128K EPROMS (certain 40-pin types). The first step was to add a pair of additional latches, which was done by replacing the 74LS378 with a 74LS377. The elimination of the old jumper farm allowed me to place it in the same relative position as the 378--and the cartridge case will still close nicely with it in place.

 

The next problem was getting a 42-pin EPROM in there. The M27C160 was the basic chip I wanted to shoehorn into this thing, as it will operate as a 2MBx8 EPROM (or as a 1MBx16, which we don't want here). Some careful trace arrangements allowed me to put it into the same general area as the old 32-pin socket--again with no impact on the ability of the cartridge case to close. Now came the fun part. The 1Mx8 chip uses the same pinout as the 2Mx8 chip, but the weird things with these chips is that the most significant address bit is always on pin 30. Time to build a new jumper farm. Now I have two jumpers, one for each of the 42-pin chips used.

 

Some more research indicated that there is a series of 40-pin chips that uses an identical pin-out scheme, so long as one ignores pins 1 and 42 of the larger chips. I could now support smaller chips with very little change to the layout while doing it. The smaller chips are available in 512K, 256K, and 128K sizes, and the ability to support them adds just three more jumpers. Now I have a 128K to 2MB board, ready for all kinds of programming goodness.

 

Assuming the menu is extensible to this level, this would allow us to put all four of Gazoo's game cartridges onto a single cartridge.

 

The layout is complete, but I still have to go over it to validate each and every connection to make sure I didn't miss anything. I'll probably do a test run of them in a month or two. . .maybe in time for Chicago.

 

I can only do 40 pin max chips. Will the board work with a 1 meg 27C080?

 

Gazoo

[+Ksarul]

At the moment, it will work with the following chips: M27C160 (2M), M27C800 (1M), M27C400 (512K), 27C4100 (512K), 27C2100, (256K), and 27C1100 (128K). All use the same style pin-out, so adapting the board to each of them was a snap. Only the first two chips are 42-pin, the rest are 40-pin. Unfortunately, the 27C080 uses the pinout style from the smaller EPROMs used on the earlier boards. It is completely different from these, so it won't work. And reading through a couple more datasheets today, I'll have to move some things around in any event--it appears that pin 30 is actually the LSB, not the MSB, which may actually make my jumper farm much easier to manage. . .

[Omega-TI]

I love it, some totally insane amounts of stuff going on to cartridges!

[dphirschler]

Just wow. I want in on this!

 

 

Darryl