Where to get the right eproms

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jacklucard
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Where to get the right eproms

Post by jacklucard »

I've been wanting to make a reproduction cartridge for a Castlevania hack but I don't want to kill another game in the process. Does anyone know where I should look?
lidnariq
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Re: Where to get the right eproms

Post by lidnariq »

First question: "where to get a PCB without removing the ROMs from an existing game"-

Depends on the specific Castlevania hack.

If it's based on CV1, you can get UNROM reproduction hardware from several places, including INL, retrostage.

If it's based on CV2, currently INL's MMC1 reproduction is out of stock, but retrostage still has something. Unless you're specifically looking at bisqwit's retranslation, in which case all this advice is irrelevant.

If it's based on CV3, you're mostly out of luck; there's no reproduction MMC5 or VRC6 available.

Second question (in the subject): "where to get the right ROMs"-

This is only relevant if you're buying from retrostage or scavenging parts from an existing PCB. With INL's board you should use his Kazoo programmer.

I'm partial to using all new flash EEPROMs, like the SST39SF0x0 parts. You can buy them from Microchip directly; they're usually cheaper than any of the electronics supplies distributors. Make sure you buy the DIP one of the size you need.

You'll also need a programmer. The cheapest options seem to be the MiniPro USB programmer and the Willem parallel port programmer.
jacklucard
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Re: Where to get the right eproms

Post by jacklucard »

Oh I forgot to mention I was going to attempt to create my own circuit board

https://www.youtube.com/watch?v=tWnfnt2rNO0

I've got everything else planned out even to making a mold for producing a cart, and no worries I'll invest in a programmer if I can find where to get the right eproms for a reasonable price.
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Memblers
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Re: Where to get the right eproms

Post by Memblers »

The SST39SF will be cheaper than EPROMs, it's like $1 for 512kB. Maybe unless you find used ones on ebay or something, then you need to erase them and stuff, kind of a hassle.

Seems like the cost of a cart mold would dwarf any EPROM costs. You know there are like 5 different cart molds made recently, at least 3 of which individual carts can be bought from?
jacklucard
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Re: Where to get the right eproms

Post by jacklucard »

(a little confused) so this SST39SF will fit in place of an eprom? And lol I'll figure something out my main goal is to create a repro without killing another game. I appreciate the responses though.
lidnariq
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Re: Where to get the right eproms

Post by lidnariq »

There's a chance it could be cheaper to get a board made at some board house (look at pcbshopper.com ) then to buy all the parts to do it yourself. Plus you won't have to worry about how to safely dispose of Copper/Iron Chloride, which is kind of a pain.

It's really easy to accidentally screw up the photoresist exposure stage of classic blacklight-based PCB making. Bad alignment and incorrect exposure time are both extremely easy pitfalls.


The SST39(S)F series are a kind of EEPROM, specifically NOR Flash. The pinout is very slightly different than a classic UV EPROM.
jacklucard
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Re: Where to get the right eproms

Post by jacklucard »

I'll take my chances :twisted: I would do that but I've noticed that the boards being sold online go through 2 phases
*Out of stock
and
*Discontinued
So basically I could still fit them in the pin holes with maybe a slight bend of the pins?
lidnariq
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Re: Where to get the right eproms

Post by lidnariq »

The SST39 series EEPROMs have the same pinout as any 128 or 256 KiB UVEPROM. The only exceptions are that the SST39SF040 (512KiB) has A18 in a different place and there is no 1MiB SST39 part.
jacklucard
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Re: Where to get the right eproms

Post by jacklucard »

Thank you, :D
sorry to be annoying but could you enlighten me on these?
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tepples
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Re: Where to get the right eproms

Post by tepples »

This board is MHROM, a variant of GNROM.

The 74HC161 IC at the top is the mapper. It controls which part of the PRG ROM is visible to the CPU at any given time and which part of the CHR ROM is visible to the PPU at any given time. It does this by setting the upper address lines going to both memories to values written to the chip by the CPU.

The 6113 IC at the left is the key chip. It cryptographically authenticates with the lock chip in the front-loading NES. If authentication between these Checking Integrated Circuits (CICs) fails, the lock chip will reset the CPU and PPU every second or two. This lockout mechanism and other practices formed the basis of a successful antitrust suit by U.S. states against Nintendo[1] as well as a privately settled lawsuit by American Video Entertainment, a division of electronic component maker Macronix.[2] (Incidentally, Macronix would go on to manufacture ROMs in licensed Game Boy Advance Game Paks.) But in the late 2000s, the CIC was publicly reverse engineered, and functionally compatible clones are available.

[1] Robert E. Tomasson. "Nintendo to Pay $25 Million In Rebates on Price Fixing". The New York Times, 1991-04-11.
[2] The Story of American Video Entertainment
jacklucard
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Re: Where to get the right eproms

Post by jacklucard »

Oh crap I just realized that this wasn't the pic I thought it was, I meant this one
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tepples
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Re: Where to get the right eproms

Post by tepples »

This board is UNROM. It has a RAM instead of the CHR ROM, and its mapper circuit cannot swap CHR memory. Instead, the 74HC161 controls which 16 KiB page of PRG ROM is swapped in at $8000-$BFFF, and the 74HC32 ensures that the last 16 KiB page in the cart is always visible at $C000-$FFFF. Games will swap a page of PRG ROM containing graphics data into $8000-$BFFF and then either copy or decompress the data to the CHR RAM through the PPU.
jacklucard
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Re: Where to get the right eproms

Post by jacklucard »

Is it possible to obtain these for programming?
lidnariq
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Re: Where to get the right eproms

Post by lidnariq »

It is possible to purchase 74'161s and 74'32s, yes. They are not programmed, rather they are single-function ICs.

Have a look on octopart or findchips.

You can find them in a variety of packages and a variety of "technologies" (the letters in the middle). You'll want a technology of LS, HC, HCT, AC, or ACT.
jacklucard
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Re: Where to get the right eproms

Post by jacklucard »

Thanks guys :D :beer: :beer: :beer:
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