What type of ROM are used in Retro Carts?

Over at a different Forum we got into a friendly debate about Bit Rot. with several people saying that eventually all Retro games will be unplayable.

I looked into it and it seems my initial assumtions were true. Of the various ROM types I think Eprom is the only one that will have it's date fade over time just exposing it to sunight for example.

I found no such data on PROM though. I assume all carts From the NES Era onward used PROM correct?

I showed these peeps a video of an NES being subermged, left outside in brutal Canadian weather, dropped, washed drilled through and still working.

So what kind of Rom are inside all these retrocarts anyway? I'm thinking in 50 years when all our discs are scratched we'll still have our beloved retro carts.

 

Cartridges use MASK ROM, they are not subject to "bit rot" any more than a processor.

 

I knew somebody here would know

 

Only thing to worry about are EPROM/EEPROM proto carts, some very small runs of commercial games that use EPROMs, and lithium cells in carts with SRAM. The batteries given time will leak all over the board and eat through it.

Almost all carts made in any quantity are manufactured with a mask process (custom silicon generated for each unique ROM) and not vulnerable to anything, at all.


Legitimate concerns are suicide batteries on some arcade PCBs (both encrypted code, and chemical-leaking NiCds), bubble memory, and hard drives used in arcade PCBs.
All magnetic mediums are at somewhat of a risk, depends on the storage conditions.

 

I know sunlight will hurt Eproms and magnetic media is at high risk.

How would one store say a hard drive to leave it less vulnerable to data loss?

 

Sure also PROMs have their predestinated lifetime, and will cease to be once as everything does.

Most manufacturer do guarantee a MTBF (Mean Time Before Failure) of around 20 years on their OTP ROMs (One Time Programable ROM). Up from that, it is put into god's hand of how much longer the media will last, like just few years or up to decades.

Here it becomes very important of how the media is used, storaged, handled, treated etc.

There are still Military Qualified PROMs which may have a larger MTBF, but I doubt that some of those were used in video game cartsdue to a much higher price.

btw. Used OPT PROMs in video game industry do usually not have deticated silicon layers for their stored program. They were written just once, by means of blowing away fuses in an array, done by a very short high voltage pulse to the accurate fuse.

e.g.:
a blown fuse = 0
an intact fuse = 1

This is an irreversible act.

 

PROM memory are still more expensive than MASK-ROM.
That's why most memory used on things like, for example NES/Famicom or SNES carts are MASK-ROM instead of PROM.

There's two types of PROM memory:

Fuse PROM
OTP EPROM

Fuse PROMs work as Tatsujin described. OTP EPROM are just EPROM dies on EPOXI encapsulation, which means they cannot be UV erased but can still bit rot.

Again, it's INSANE to use programmable memory (Even of OTP type) on games that will have large production runs. Some even use special MASK-ROM chips with built in memory mapping circuitry like for example those 1-chip Sega MASTER SYSTEM/Game Gear cartridges.

 

mask roms can fail, though it's probably more likely that something else will fail first.

eventually your nes will die and you won't be able to get parts to repair it.

 

Just bumping an (apparently dead thread) I've stumbled today into an failed Famicon Parodius cartridge which suffered of BIT-ROT on it's PRG rom.

Konami Part number:
RC849J00P

OEM PN:
RRP231027D (Ricoh MASK ROM ?)
5958 0KC 47

I downloaded two Parodius DA! FC roms (until I found one that matched the program revision on this cart) then I programmed an SST 29EE010, made the proper pin lifting and soldered it back to the cart.

Game works properly now as it was expected.

2nd half of the MASK ROM has random reads at fixed addresses in a periodic/suspicious interval, which suggests a failure of the address decoder at the second mask rom bank. (I suspect this chip has two banks of 64KB)


I never expected to see it myself.

So, yes BIT-ROT happen on mask roms too........ :banghead:

 

I've seen a SNES title with a mask rom that had what appeared to be bit rot, though it could also have had some sort of particle accelerator pointed right at the section where graphical data was being stored.

 

Yes, data decays, from what I remember when I was reading data sheets, it's upto 100 years lifespan you get on them.

 

I'd imagine the data itself doesn't so much decay as the storage medium itself decays. I honestly don't know off hand how mask roms store their data but from what little I understand it would seem that if the material decays then it wouldn't be accessible or accessed correctly. Backup, backup, backup!

 

It's possible the cartridge was defective if you don't know that it ever worked.

Are you sure there just wasn't a cold/bad solder joint between the MaskROM and the PCB? Basically did you exhaust all options and are sure the MaskROM was actually at fault?

 

I extracted the PRG mask ROM, read it and compared with existing "ROMz" on the internet. I even figured out that there is two revisions of the game.

This one in particular was of the second batch. The ROM was deemed bad as it could not provide a consistent read out of the bad bytes.

In the end after replacing the chip the cart worked fine so it's proven the MASK rom is bad. And I believe it's an HITACHI made part instead of "Ricoh" as the website with NES/FC ROM database identifies it.