Hi,
I've made a SNROM devcart and the only the I need to test it is the EPROM chip. But I can't find any 27C256 chips with 32 pins.
Does anyone know where I can order some. I've looked everywhere.
If you're looking for 256kb, it should be 27C2001, not 27C256, I think.
27C256 is for 256 kilobits, wich is 8 times less than what you need.
27C256 only come in 28 pin PDIP. Why would you want to use a 32 KByte EPROM anyway in a SNROM which can handle up to 512 KBytes? You could reroute some of the pins to handle a 28 pin EPROM but it would be better just to put the game code into a larger EPROM. Are you using your own code? You could always fill a larger EPROM with copies of your code so the interupt vectors will always be in the right place. I've never heard of a SNROM game with less than 128 KBytes of memory.
Lloyd Gordon wrote:
27C256 only come in 28 pin PDIP. Why would you want to use a 32 KByte EPROM anyway in a SNROM which can handle up to 512 KBytes?
The MMC1 is not capable of natively addressing more than 256 KBytes of PRG ROM unless you use a special setup like in SUROM/SVROM (where it uses one of the upper CHR ROM select lines to choose a 256KB PRG bank).
27C256, that's odd, beacuse all of the 27C256's I've seen on the internet have 256k. Which is what I wanted. This EPROM pinout chart gave me the impression that they made 32 pin ones.
So, 32k x 8 doesn't mean 256k?
EDIT : I thought they meant byte, not bit. Futerlec sells 27C2001. But the pinout doesn't match what I need. Which specific one will work?
32 kilobytes * 8 bits per byte = 256 kilobits (27C256)
256 kilobytes * 8 bits per byte = 2 Megabit, (27C2001), what you need.
You are forced to rewire pinout on a NES cart anyway. Only NROM cards doesn't need rewiring.
As you can tell, I'm very to new to this.
I followed the instructions I found here
http://nesdev.com/NES%20EPROM%20Conversions.txt last week. So I've already "mangled" the cartridge board.
I was just wondering if this EPROM chip will work
http://www.digikey.com/scripts/dksearch/dksus.dll?Detail?Ref=74624&Row=177322&Site=US along with the instructions I followed.
Any chip labelled 27C2001 or 27C020 should work.
I think there is no difference between the two names. There are chances it depends of the producer.
Thanks. Thanks for the help. I found a good deal on eBay, and also got a ZIF socket. Hope everything works.
Thanks again everyone.