Earthbound Zero on 27C256

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Earthbound Zero on 27C256
by jensma on 2012-11-03 (#102268)
Hey there community,

I searched the web but couldn't find an answer to my problem. Maybe you guys can help me. I did some SNES-Repros in the past but I'm new to the NES :)

I'm about to build an Earthbound Zero for my collection. Is it possible to burn it on two 27C256's? The PRG and the CHR-File are 256kb in size.

If it is burnable, how to connect the eprom to the PCB?

I got this information from this site:

Quote:
TKROM & TSROM (mapper 4):
PRG socket:
Bend up pins 1, 2, 24, 30 and 31 (or cut tracks 2, 24, 30 and 31)
Solder pin 2 to hole 24 (A16)
Solder pin 24 to GND (OE)
Solder pin 30 to hole 1 (A17)
Solder pin 31 to hole 2 (A18)
CHR socket:
Bend up pins 1, 2, 22, 24, 30, 31 (or cut tracks 2, 22, 24 and 30)
Solder pin 2 to hole 24 (A16)
Solder pin 22 to hole 31 (CE or CHR /A13)
Solder pin 24 to hole 2 (OE or CHR /RD)
Solder pin 30 to hole 1 (A17)


Well, a 27C256 has just 28 pins, so erm.. I don't have to mind the information about what to do with pins 30 and 31, right?

Any help is highly appreciated :)
Re: Earthbound Zero on 27C256
by lidnariq on 2012-11-03 (#102269)
The number at the end of the part is kilobits, so a 27C256 → 32KiB. For 256KiB you'd need a 27c2001 or something equivalent.
Re: Earthbound Zero on 27C256
by jensma on 2012-11-03 (#102270)
lidnariq wrote:
The number at the end of the part is kilobits, so a 27C256 → 32KiB. For 256KiB you'd need a 27c2001 or something equivalent.


Damnit, I felt for the '256' :/ Thanks for the info :)
Re: Earthbound Zero on 27C256
by 3gengames on 2012-11-03 (#102271)
27C256 is a 32KB chip. And the ROMS you slit aren't kb, they are KB. Bytes. You'd need 8x 256's for each program and characrer side. You need a 27C020 for *EACH* side. And there should be wiring sheet on the front page. You should be able to work on from there.

ETA: Tokumaru has a point.
Re: Earthbound Zero on 27C256
by jensma on 2012-11-03 (#102272)
3gengames wrote:
27C256 is a 32KB chip. And the ROMS you slit aren't kb, they are KB. Bytes. You'd need 8x 256's for each program and characrer side. You need a 27C020 for both sides. And there should be wiring sheet on the front page. You should be able to work on from there.


Got it, thanks a lot!

You guys are great :)
Re: Earthbound Zero on 27C256
by socram8888 on 2012-11-03 (#102274)
You can use FLASH (29F) instead of EPROM (27C). It is cheaper.
Re: Earthbound Zero on 27C256
by tokumaru on 2012-11-03 (#102275)
3gengames wrote:
You need a 27C020 for both sides.

You can't put both PRG and CHR in the same chip though, it has to be 2 chips.
Re: Earthbound Zero on 27C256
by jensma on 2012-11-04 (#102296)
tokumaru wrote:
3gengames wrote:
You need a 27C020 for both sides.

You can't put both PRG and CHR in the same chip though, it has to be 2 chips.


Yep, I know :)

socram8888 wrote:
You can use FLASH (29F) instead of EPROM (27C). It is cheaper.


Mhh, yeah, you're right. I never thought about that, I always used eproms for repros. And my willem seems to be able to burn the 29F* without any additional adapter.. that's cool :D And they're indeed way cheaper than the eproms. Thanks for this great hint!
Re: Earthbound Zero on 27C256
by FrankWDoom on 2012-11-04 (#102298)
socram8888 wrote:
You can use FLASH (29F) instead of EPROM (27C). It is cheaper.


what are the part #'s for 29 series 2 mbit chips? and where do you buy them that they are cheaper than eproms?
Re: Earthbound Zero on 27C256
by 3gengames on 2012-11-04 (#102299)
29F020, and anywhere that has chips? :)
Re: Earthbound Zero on 27C256
by socram8888 on 2012-11-04 (#102311)
Use 29F040 or 28F020. They are both on eBay for less than 4USD each with shipping.
Re: Earthbound Zero on 27C256
by qbradq on 2012-11-04 (#102324)
If you're looking for a source other than eBay for whatever reason I would recommend Futurlec. They have decent prices, very reasonable shipping (that's a recent change, used to be not so good) and decent customer service. They also have a lot of supplies and protoboards and such at great prices.
Re: Earthbound Zero on 27C256
by jensma on 2012-11-11 (#102715)
socram8888 wrote:
Use 29F040 or 28F020. They are both on eBay for less than 4USD each with shipping.


Thanks for the hint - I built Erthbound Zero today with two 27c020. Next time I'll use Flash ROMs :)

qbradq wrote:
If you're looking for a source other than eBay for whatever reason I would recommend Futurlec. They have decent prices, very reasonable shipping (that's a recent change, used to be not so good) and decent customer service. They also have a lot of supplies and protoboards and such at great prices.


Thanks for the link - I'll bookmark it & ask how much shipping to germany would be :)
Re: Earthbound Zero on 27C256
by qbradq on 2012-11-11 (#102744)
Oh, Germany :D There's a lot of good suppliers in the EU. Others on this board would better know which ones carry vintage parts. I've never looked into them much due to the shipping.