Mask rom pin 35

[Markfrizb]

Is pin 35 (A22?) of the mask rom used for anything? It connects to cart edge 48.

[qwertymodo]

Well, cart pin 48 is A23, so it could be used for a 64Mbit ROM...

[Markfrizb]

Ok. But I thought there weren't any 64m mask roms. And pin 48 just goes to mask rom pin 35. And that is on both Lo and Hi rom carts (1A3M and 1J3M carts). So how would cart A23 (pin 48) assert a 64mb address? Or am I missing something?

The bigger picture.... I'm making a rom adapter using 2 27c322 EPROMs and for the larger than 32mb games, how would the cart access the next 32mb bank?

Thanks!

[lidnariq]

The only difference between the mode 21 ("HiROM") memory model and the mode 25 memory model ("ExtHiROM", I think?) is whether or not A23 is used to decode things differently between the top and bottom 8MiB of address space. Neither use A22 for anything. There were very few 5 or 6MiB games, and none larger, and the two of those five that didn't use a coprocessor are mode 25.

Using A23 makes a Mode 20 ("LoROM") cart into ... well, something non-standard.

[Markfrizb]

The only difference between the mode 21 ("HiROM") memory model and the mode 25 memory model ("ExtHiROM", I think?) is whether or not A23 is used to decode things differently between the top and bottom 8MiB of address space. Neither use A22 for anything. There were very few 5 or 6MiB games, and none larger, and the two of those five that didn't use a coprocessor are mode 25.

Using A23 makes a Mode 20 ("LoROM") cart into ... well, something non-standard.

thank you. Let me switch gears.... there is a SMW hack that is 48 mbits. "Demo World : The Legend Continues" (DW:TLC), it's a full hack of Mario World that's complete right to the end. http://fusoya.eludevisibility.org/lm/dw.html
since this game is bigger than the Lo rom standard, I assume that it uses the hi rom model. Has anyone put this on an actual cart? I'm really wanting to design my adapter to be as versatile as possible. 32, 48, 64 and possible 96mbits. I can put a decoder on the pcb but I don't know what is the best way to make it versatile.....should A22 (rom) = cart A23 -- be run to the decoder (139) or something else? Any suggestions??

Thanks!

[lidnariq]

In the readme, he says it's "exhirom", or mode 25.

The patch is old enough that you should make sure it works in bsnes before taking a chance on it not working in hardware.

To put this on hardware, you'll probably want to use a 74'139 on A23 to select between two ROMs, the first 4MiB is used as normal for mode 21 (when A23=1), the last 2MiB mapped when A23=0. Skip A22 from the SNES; do connect A15.

[getafixx]

I believe this info has been covered before, but I didn't look for it on here. It is available over on racketboy though.

http://www.racketboy.com/forum/viewtopi ... &start=410


See further down that page for pictures.

[Markfrizb]

Thanks!

[Markfrizb]

Update: ok, built a small double rom tester board that I can reprogram easily. Switches on the top of the tsop adapter control the CE lines between the 2 roms (so I can reprogram them while connected to each other)

The "super demo world - legend continues" is 48mbits and A23 (MASKrom pin 35, cart pin 48) controls which rom is selected using a 74xx139.


Next, I tried DQ3 English which is also 48mbits and it uses A23 (pin 35 from mask rom - cart pin 48) to switch between the 2 roms using a 74xx139. Picture is perfect, no glitches and save ram works as it should.

Last question... What other games (non-special chip ones) are 48 or 64mbits?

Thanks

EDIT: Tales of Phantasia (Jap) also uses A23 as rom select (using a 74xx139 of course). But I can't seem to get the English version translation to work :/

[Markfrizb]

Here's what the super demo world look like..



Edit #2: Got it working using A23 like the others.
I split the rom wrong somehow.... But it now works like the other ExHiRom games.