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UNROM programmed cart

UNROM programmed cart
by on (#21897)
I have read tons of tutorials on how this is done, I just have one question left if my rom image doe not contain any CHR.bin information eg: CHR 0Kb does this mean I do not have to remove the CHR chip from my donar cart just the PRG.
Also if jumped the gun and removed the CHR chip before I knew what I was doing can I just replace it with a blank 27c64.

thanx eh

My goal for my virgin attempt at cart programming is to make my own copy of California Raisins.

Oh and bye the way im sort of new here Ive been reading this site for quite sometime I just didnt register till today.

Thanx for all the info and help you have on this forum.
Re: UNROM programmed cart
by on (#21899)
marvelus10 wrote:
if my rom image doe not contain any CHR.bin information eg: CHR 0Kb does this mean I do not have to remove the CHR chip from my donar cart just the PRG.

Yes, if there is no CHR data the game uses CHR-RAM, so the CHR chip in the cart is RAM, that is controlled by the program itself, and you don't need to touch it at all. This is the case with all UNROM games.

Quote:
Also if jumped the gun and removed the CHR chip before I knew what I was doing can I just replace it with a blank 27c64.

That wouldn't work, because the 27Cxxx are ROMs, they are erasable with UV light, yes, but still ROM. The program won't be able to store anything there, and the graphics would look all wrong.

You should either put the original RAM chip back (if it wasn't destroyed when removed) or a similar RAM chip. Chips used as WRAM in games such as SMB3 would work. Of course, any other CHR-RAM game will have the chip you want. But if you are to use another cart, you'd better get another UNROM one, just forget about the other one and do it right this time around.

Have you removed the CHR-RAM chip? Was it damaged?

by on (#21900)
All unrom-based games use, instead of vrom, one single sram chip (usually an 6420, but I've seen 6116's work fine) alongside a PROM for the PRG-ROM. If you still have that chip floating around, you might want to place it back in, since programs made for the unrom boards only have PRG-ROM data stored on one chip.

It can't be replaced with a blank 27c64 since those chips require not only a programming voltage, but also can only be programmed once before needing to be erased, in this case with an ultra-violet light.

by on (#21902)
Huh? The generic 8K x 8 SRAM is 6264; 6116 is 2K x 8.

by on (#21903)
Great thank you, I put the CHR RAM back in the cart lets hope I didnt bugger it up resoldering it.

While I have the attention of some pros. here, these are examples of what im reading.
· Desolder the PRG chip from the board.
· On the EPROM, bend up pin 1, 2, 24, 31, 32.
· Solder the EPROM onto the board where the PRG rom was.
· Place wire from pin 1 to pin 30, 31, 32 on the EPROM.
· Place a wire from pin 2 to hole 24 on the board.
· Place a wire from pin 16 to pin 24 on the EPROM.
or
UNROM (mapper 2):
Bend up pins 1, 2, 24 and 31
Solder pin 2 to hole 22 (A16)
Solder pin 24 to GND (OE)


What is right for my application.

Am I right in that this chips is the one I will need
EPROM 27C010/27C1001 128KBytes (32pin):

Is there a 28 pin chip I can program and just drop in so there will be no bending of pins. I want this to be a permenant application to, no need to be pulling the chip out and reflashing with another game.

thanx eh

by on (#21906)
Quote:

Is there a 28 pin chip I can program and just drop in so there will be no bending of pins.

No, there is not. Nintendo didn't need the /OE pin, nor they needed VPP because the chip were factory programmed. So they could reduce the number of pin down to 28, and they could made the UNROM board smaller (UOROM is the equivalent with 32 pin PRGROM, allowing up to 256kB. So if you really don't want to bend up pins, the only way to go is to found an UOROM game (that is MUCH, MUCH rarer).

EDIT : You could just go the lazy way and order a UNROM board from Memblers Industries (aka Memblers). You won't need any rewiring or anything, just solder the ROM down. However, I think it'd be somewhat more expensive.

by on (#21967)
Well it seems I have got myself into a real pickle with eprom values etc..

When I view my rom with the current version of NEStopia i get this:

System: NTSC
Board/Chips: UxROM
Mapper: 2
PRG-ROM: 128k, CRC: 0xF2096D9C
CHR-RAM: 8k

So I assumed this meant that I would need this eprom:

27C128 128k (16k x 8-Bit) EPROM

However I read some more and came across some text and got it into my head that this may be the eprom I should be using:

27C1001 200ns 1Mb (128k x 8-Bit) EPROM

So call me dumb laugh at me all you want but please give me a straight answer, as I am new to this and this will be my first atempt at making myself an unreleased cart.

thanx eh

by on (#21968)
Yes, 27C1001 is the one you want. 27C010 is the same, too.

by on (#21972)
Quote:
So call me dumb laugh at me all you want but please give me a straight answer

Well, the dumb is the EPROM retailer that doesn't make a clear difference between kilobytes and kilobits.
128 kilobits is 16 kilobytes, and that won't be large enough. However, 1 Megabits is 128 kilobytes, wich is the one you want to programm an UNROM game.

by on (#21974)
Awsome guys thank you very much.