Tailsnic Retroworks
Professional
Hi. I have made a provisional schematic of how I think P2 rom latching works on Vortex cartridges with games higher than 1MB+4MB total CPU size, targeted to PROGBK1 original boards.
The idea is to add a new LS74 for latching D2 signal, which can improve P2 from 4MB to 8MB using the same logic as 64mbit C ROMs. (CE signal now is A21 new input bit). These following games are an example of big exceeding P2 4MB rom size:
Rage of the Dragons
Samurai Shodown V Special
SNK VS CAPCOM Chaos
The King of Fighters 2003
Theorically, catching the first 1MB of the joint PROM file of Vortex rom would be P1, and the rest of the info would be P2 (max 8MB). This is a test I want to do, but first I want to know if anyone knows if this type of latching is used in Vortex roms.
I have studied this possibility because I have seen in original roms that normally would use 1 x 27C160 PROM on P1 (2MB), the normal banking is catching the second MB as the main MB and the first MB as the banked MB. In Vortex roms this MBs are interchanged for following the logic of first MB - main MB, and the rest of the info as P2 ROM.
I don't think the new BANK2 signal has to be used on LS139 input logic for adapting P2OE signal, because by default P2OE signal is PORTOE (joint logic from PORTOEU and PORTOEL from LS08. ) It has nothing to do when referring to BANK0 and BANK1 signals, so BANK2 shouldn't be a problem to add.
Could it be possible to adapt bigger games to that logic/banking or are they adapted already?
The idea is to add a new LS74 for latching D2 signal, which can improve P2 from 4MB to 8MB using the same logic as 64mbit C ROMs. (CE signal now is A21 new input bit). These following games are an example of big exceeding P2 4MB rom size:
Rage of the Dragons
Samurai Shodown V Special
SNK VS CAPCOM Chaos
The King of Fighters 2003
Theorically, catching the first 1MB of the joint PROM file of Vortex rom would be P1, and the rest of the info would be P2 (max 8MB). This is a test I want to do, but first I want to know if anyone knows if this type of latching is used in Vortex roms.
I have studied this possibility because I have seen in original roms that normally would use 1 x 27C160 PROM on P1 (2MB), the normal banking is catching the second MB as the main MB and the first MB as the banked MB. In Vortex roms this MBs are interchanged for following the logic of first MB - main MB, and the rest of the info as P2 ROM.
I don't think the new BANK2 signal has to be used on LS139 input logic for adapting P2OE signal, because by default P2OE signal is PORTOE (joint logic from PORTOEU and PORTOEL from LS08. ) It has nothing to do when referring to BANK0 and BANK1 signals, so BANK2 shouldn't be a problem to add.
Could it be possible to adapt bigger games to that logic/banking or are they adapted already?
i'm really interested.