Thomas Jentzsch Posted April 10, 2022 Share Posted April 10, 2022 Thanks for the explanation. That seems to fit to the existing ROM's code. Since the ROMs are 1:1 conversions from Parker's E0 bankswitching, they always switch only one segment. Quote Link to comment Share on other sites More sharing options...
alex_79 Posted April 10, 2022 Share Posted April 10, 2022 Yes, I can't imagine that "feature" to have any practical use. I think it's simply the result of this specific board design, and the code is supposed to only set either A4 or A5 or A6 to zero when bankswitching. Quote Link to comment Share on other sites More sharing options...
Thomas Jentzsch Posted April 10, 2022 Share Posted April 10, 2022 I suppose this was cheaper to build than the original Parker scheme? Quote Link to comment Share on other sites More sharing options...
alex_79 Posted April 10, 2022 Share Posted April 10, 2022 I imagine it to be the case, although I don't know how the scheme was implemented in the original PB games. Quote Link to comment Share on other sites More sharing options...
Thomas Jentzsch Posted April 10, 2022 Share Posted April 10, 2022 AtariProtos.com has a prototype board picture. 1 Quote Link to comment Share on other sites More sharing options...
alex_79 Posted April 10, 2022 Share Posted April 10, 2022 Thanks. That proto uses 5 ICs compared to 4 in the board shown in this thread, so I guess it's a bit more complex and expensive to build. Quote Link to comment Share on other sites More sharing options...
Thomas Jentzsch Posted April 11, 2022 Share Posted April 11, 2022 (edited) 12 hours ago, alex_79 said: Thanks. That proto uses 5 ICs compared to 4 in the board shown in this thread, so I guess it's a bit more complex and expensive to build. And two of the 5 ICs might be more complex, no? They have 20 instead of 16 pins. Here is another board, that looks pretty simple. Or is the IC something more expensive? Or maybe this early demo is only 4K? Edited April 11, 2022 by Thomas Jentzsch Quote Link to comment Share on other sites More sharing options...
alex_79 Posted April 11, 2022 Share Posted April 11, 2022 1 hour ago, Thomas Jentzsch said: And two of the 5 ICs might be more complex, no? They have 20 instead of 16 pins. Yes, I think that larger ICs would typically be more complex and cost more, although the availability probably plays a role on the price too (Common parts are cheaper). I'm no expert, though. 1 hour ago, Thomas Jentzsch said: Here is another board, that looks pretty simple. Or is the IC something more expensive? Or maybe this early demo is only 4K? The latter. The 24 pin EPROM is 4K. The 74LS04 is an inverter used to invert A12, as EPROMs usually have an active low "Chip Enable" pin. 1 1 Quote Link to comment Share on other sites More sharing options...
alex_79 Posted April 11, 2022 Share Posted April 11, 2022 I drawn a (hopefully correct) schematic of the Bankswitching logic found in the board shown in this thread: schem_PB_Brazil.pdf 1 Quote Link to comment Share on other sites More sharing options...
Thomas Jentzsch Posted April 11, 2022 Share Posted April 11, 2022 (edited) Cool! Thanks! @cetics (whenever you should come online again ) Do we know the brand which was using this board? BTW: The two games are Montezuma's Revenge (01.bin) and Popeye (02.bin) (both 100% identical to the NTSC releases, except for the hotspots). Atarimania has no 2 in 1 with these two games listed. Edited April 11, 2022 by Thomas Jentzsch 1 Quote Link to comment Share on other sites More sharing options...
cetics Posted May 30, 2022 Author Share Posted May 30, 2022 Thanks for the answers. I think I still have the cartridge in my collection, but it never worked, so I was afraid to invest and ask for a PCB to be manufactured in China. Because I wasn't sure if the dumps were good. I found a similar board (working) on the Brazilian market a while ago and thought I'd buy it to see what was wrong with mine, and try to export the working schematic. But the price they asked was simply impossible to pay back then. Today I looked and couldn't find it anymore. I'm thinking of redesigning the board and ordering a PCB in China for testing. Quote Link to comment Share on other sites More sharing options...
cetics Posted May 30, 2022 Author Share Posted May 30, 2022 Fotos e DIP.zip Here are the photos of the board I made at the time and an attempt to redraw the board in dip trace (with source file). It may be necessary to check as I may have made some mistake (no tests) 1 Quote Link to comment Share on other sites More sharing options...
cetics Posted May 30, 2022 Author Share Posted May 30, 2022 In this video (52:12) the owner of the channel shows a similar board working. Quote Link to comment Share on other sites More sharing options...
Thomas Jentzsch Posted August 5, 2023 Share Posted August 5, 2023 Support for these ROMs will be added (as "03E0") with the next Stella release. 3 Quote Link to comment Share on other sites More sharing options...
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