so I have made over almost 30 repros for myself now and the only problems I have ever had is with SNROM boards. only 1 has ever worked for me and that was when I made outlands. I made a sweet home, cocoron and a mega man 2 rom hack and none of them work right. with the mega man hack and cocoron it will boot properly then randomly freeze very early every time and never in the same spot. then sweet home just boots to gray screen.
I have used different souces of eproms and each are on a different board (the mega man 2 hack is the snrom board with no battery).
the only connection the failing games share is their original roms are 256kb while outlands is 128kb and outlands is the only one to work so far
Outlands is the only one I used a 27c010 for and didn't have to double it's size with famirom. All the 256kb games are being doubled with famiROM program which I use for everything and have only ever had issues with these snrom games(so I dont know if its related but I thougt I should mention it anyways)
what chips are you using for the 256KB games? famirom should tell you to use a 27C020 or bigger and it should only be splitting, not doubling anything (* if you're not using oversized chips). How big is the output file? How are you wiring up the chips?
Putting a 256 KiB program on a 27C040 or 29F040 requires splitting off the iNES header and then doubling the result. Or you can instead not double the PRG ROM and then ground A18.
tepples wrote:
Putting a 256 KiB program on a 27C040 or 29F040 requires splitting off the iNES header and then doubling the result. Or you can instead not double the PRG ROM and then ground A18.
Shouldn't you still ground it either way? Isn't a floating address pin problematic?
Some instructions recommend soldering the high address pins to +5V instead of GND. This requires prepending the correct amount of data to the ROM image, and as I understand it, the easiest way for the user to understand how many bytes to prepend and how to go about doing so is just to double up the data to fill the memory.
My question wasn't whether to use 5V or Ground, it was whether using neither and floating the line would be a bad idea.
As far as doubling the ROM, that's simply the most sensible thing to do, regardless of how you deal with the extra address line.
In practice there doesn't seem to be any issue with leaving an address line floating although I typically don't build that way.
FrankWDoom wrote:
what chips are you using for the 256KB games? famirom should tell you to use a 27C020 or bigger and it should only be splitting, not doubling anything (* if you're not using oversized chips). How big is the output file? How are you wiring up the chips?
27c4001 and 27c040. Same issue on both. Famirom doubles the file to fill the chip as they are normally half the size of the 27c040. I do this with every game I have made and have had no issues besides with snrom games
tepples wrote:
Putting a 256 KiB program on a 27C040 or 29F040 requires splitting off the iNES header and then doubling the result. Or you can instead not double the PRG ROM and then ground A18.
Can you explain the not doubling part more? Does this mean just doubling the Rom using famirom will cause issues if you follow the standard wiring instructions found on this site?
Bernkastel_Kues wrote:
Can you explain the not doubling part more? Does this mean just doubling the Rom using famirom will cause issues if you follow the standard wiring instructions found on this site?
"Not doubling" means you fill the other half of the EPROM with garbage, or all 1s, or all 0s. Tying A18 to ground means that the second half will never be accessed.
Unless you have a good reason not to, you should just double the ROM to fill the space. You should
also tie A18 to ground or 5V to keep it stable.
in that case doubling is fine/recommended. how are you doing your wiring?
do you use your 4 megabit chips for other 2 megabit games? do you have any trouble with those? I wonder if it's a quirk with famirom. I wouldn't expect that to be a common usage scenario, although there's nothing about it that it should be inherently problematic.
FrankWDoom wrote:
in that case doubling is fine/recommended. how are you doing your wiring?
do you use your 4 megabit chips for other 2 megabit games? do you have any trouble with those? I wonder if it's a quirk with famirom. I wouldn't expect that to be a common usage scenario, although there's nothing about it that it should be inherently problematic.
Works fine with all other 2Mb games. I write it according to the chart found on this site (which I don't have access to atm)
Here's the wiring for SNROM:
SNROM (mapper 1):
Bend up pins 1, 2, 24, 30 and 31 (or cut tracks 2, 24 and 30)
Solder pin 2 to hole 24 (A16)
Solder pin 24 to GND (OE)
Solder pin 30 to hole 1 (A17)
I usually leave pins floating and never had problems yet except for UNROM where A17 has to be tied to 5V when using a 32 pin EPROM.
Either way, your problem sounds like a bad connection.
I've made many SNROM repros and all of them work fine, even Sweet Home and any Mega Man 2 Hack out there.
Pictures of the cart might help.