Hypothetical Question

[Zeus]

I was recently reading the keynote speech from ADAMcon 7 in which a somewhat frightening point was made. Although he was speaking of ADAM computers and Colecovision consoles, the point is equally valid for Atari. The issue was bitrot. He said that the mean lifespan of ROMs is approximately ten years before digital degradation begins, thus meaning that by now a good number of our cartridges now have bugs, or have ceased working altogether. I think we all have experiences with dead cartridges or ones that behave stragely. This leads me to wonder, how long do we have before our beloved cartridges start dying en masse? How much longer do we have before we can expect the majority of them to be dead, and most importantly, is it really worth shelling out the big bucks for games that will be non-functioning within a few years or a decade? I'd like some answers from the more tech savvy folks out there, or anyone else who has an opinion on the matter.

[bobafett07728]

This is a very good question. I am lookign forward to the answers from our well educated forumites.

[bloatedmonkey]

After 20 years, most Atari games are still working, so I wouldn't panic too much. But I have no doubt that most of my games will be dead before I am, since I don't keep mine in an Argon-filled vault. That's why I buy and sell games, and never buy with money that I won't quickly make up by selling - that way when my games are dead and I have to open them up to replace the chips, I can't say that I lost anything but time.

is it really worth shelling out the big bucks for games that will be non-functioning within a few years or a decade?

....or you can just win rare some games in my contest! (sorry for the shameless plug).

[joeybastard]

Well I think it probably depends on how they are stored. I would imagine a hot humid climate would cause more carts not to work because decay of the actual components would happen more quickly. I would think a temperate to cool and dry place would be the best place to store carts to avoid decay. Just a guess though.

 

Honestly, I wouldn't be too concerned with it. There are carts out there going on 25 years old (1978-2003) that still seem to work perfectly. Like the lifespan of CDs I don't think we know for sure what the lifespan is because none of this stuff has existed long enough to represent an average. In the case of the ADAM, my guess is the carts will beOK for a long while, but the tapes are definetely already dying out.

[+Atarius Maximus]

Only games with EPROMS are subject to Bit Rot. Here's a quote from Tempest I found in an old thread relating to this subject:

 

 

Regular cartridges should theoretically last forever, but prototypes use EPROM's to store data. They were never meant to store this data indefinetly, it was only suppose to be temporary storage while the programmer or reviewer tested the latest code.  

 

EPROM's (Elctronically Programmable Read Only Memory) have a little window that allows them to be erased by shining an Ultra-violet light through it (this is why they're normally covered with a sticker). This ability to be programmed and erased makes them unstable over time, and eventually they subcome to what collectors call bit rot. This basically means that somehow the code on one of the EPROM's has gotten corrupted or partically erased making the prototype worthless.  

 

These prototypes were supposed to be used for a few weeks or so at a time (they got updated with new code frequently), but now we're pushing 20+ years. I'm amazed that they still work, but it's only a matter of before they go bad. The only defense against this is to have them dumped and re-program the EPROM's with the original code (making them good as new for a few more years). Certain environmental effects can make them go bad too (excessive heat or cold, static electricity, etc.). Contrary to popular belief X-Rays don't bother them at all (mine went through the airport just fine).  

 

 

[+wavemotion]

I'm happy to answer... although we do seem to go over this particular question every few months

 

The lifespan of a typical ROM cart with no other hardware taken into account is basically forever (well, not FOREVER! but long enough for you not to care). ROMs are a series of tiny fuses that are burnt to produce a pattern of 1's and 0's that cannot really be altered with time. It can, however, be damaged from a static discharge - walk across your carpet, pick up your cart and there is a teeny tiny chance you could discharge and damage the cart (usually causing an additional fuse to blow creating a different pattern than the original ROM had). But with reasonable care, this is not normally a problem. The contacts of the cart may also wear down - and some Activision carts are already doing this (I think they used thin PCBs to start with!). You can clean them if they get soiled or gummed up, but if they wear thin they won't make great contact. Still given proper care when inserting and removing from the console, this should not be much of a problem.

 

Now EPROM carts do have a theoretical lifespan as the electron charge configuration can shift over time due to entropy and cause bit pattern changes in the EPROM (UV light makes this happen very quickly which is what they use to erase EPROMS). The EPROM is a series of cells that can individually retain a 0 or a 1 value. The UV light makes all bits a 1. Programming the chip changes the 1's to 0's (as appopriate to the binary stream) by applying a charge and altering the placement of electrons in the cell (there are two transistors and a thin oxide layer between that interact with this). Given enough time, the electrons will shift/migrate due to entropy causing a data bit to shift value. It is important that to get maximum life one should cover the erase-window of the EPROM with an opaque label (and the black cart covering helps too in this case). I've read that typical florecent lights will erase an exposed window EPROM in about 3 years. Direct sunlight in about a week. Keep the window covered and storage/mounting inside the black case is recommended for maximum life.

 

If an EPROM does go bad, it can be erased and re-programmed and in theory would be good for another long life (assuming you had the original binary with which to reprogram it!). Typical ratings on EPROMS are on the order of 10 years - though that number is generally considered very conserative (typical of most specs in the EPROM chip world). Figure 20+ years anyway, as evidenced by the many EPROM carts from the early 80's that are still working. But they simply cannot hold the charge forever ... entropy will take over at some point and once the charge on any given cell starts to degrade (which is inevitable), the EPROM will go bad. It's only a matter of time... though it may be typically more than 20 years, it is probably less than 50 for most 80's vintage EPROMs.

 

Luckily, the vast majority of Atari carts use maskable ROMs which are far more hearty.

[Pitfall Harry]

Most Atari game cartridges use a ROM chip to store the game code, whereas hobbyists' homebrew games and prototypes use an EPROM chip. ROMs are not susceptible to bitrot, but EPROMs are. So nobody's collection of Atari games is going to rot away "en masse," no matter how long they wait, unless all they collect are homebrew games and prototypes.

 

 

Why are EPROMs susceptible to bitrot, but not ROMS?

 

Because of the way the each of the two types of chip are manufacuted and are designed to function.

 

A ROM (Read Only Memory) chip is designed to have it's data read and never overwritten. Ok then, so how do the 1's and 0's get into the ROM in the first place? It happens as part of the process of manufacturing the ROM. ROMs are created in layers called "masks". The set of masks for a particular ROM determines the "game code" that gets burned into it. The masks specify the geometric layout of dopants, pockets of N-type and P-type material, which will be diffused into the silicon wafer as the chip is being fabricated. The dopants are arranged to form transistors which, after the chip is powered on, are either always conducting (a binary 1) or always at shut-off (a binary 0), depending on the arrangement of the dopants.

 

The dopant regions of Atari vintage ROMs are HUGE! Which basically means they can be exposed to UV, cosmic radiation or Super-Duper-Kryptonite for millions of years and the layout of their geometry will not be compromised. As long as the dopant regions that are locked within the silicon matrix don't erode away, the transistors they form will function virtually forever. That is, so long as you don't overpower the circuitry or crush the ROM with a solid hammer blow.

 

 

An EPROM (Erasable Programmable Read Only Memory), on the other hand, is not nearly as stable as a ROM. In fact, EPROMs are unstable by design -- they are designed to be erased! The matrix of tiny tunneling capacitors within the silicon chip of an EPROM hold either a logical 1 or 0, depending on their state of charge. That state of charge may be programmed into the individual capacitors at any time AFTER the chip is manufactured. Programming the state of charge of those capacitors is how a game maker loads his game code into the chip.

 

Now, the E in EPROM means they are erasable. You can erase an EPROM (so you can reprogram it later) in a matter of seconds by exposing it to the UV light of an EPROM Eraser. The UV light causes all the capcitors within the chip to discharge, making the chip revert back to an array of capacitors with uniform state of charge. Because EPROMs can be erased by UV light by design, this means that ANY source of UV light can blank them out, given enough time for the exposure to take its toll. This is where bitrot comes from. Ambient light contains UV radiation, and exposure to ambient light, over a decade or two, can and will cause the weakest capacitors in an EPROM to spit up their charge state and flip a bit. It only takes a single bit in the wrong place to go bad to render an entire game stored in an EPROM disfunctional.

 

To protect against accidental erasure from ambient light, EPROMs usually have a sticker covering the quartz window that exposes the silicon chip within. If you have a prototype or homebrew game whose EPROMs do not have a sticker covering the little window, cover it up as soon as you can! Also, it's a good idea to keep the circuit board inside an opaque cartridge shell as further protection from UV light.

 

Despite your best efforts to protect your EPROMs from exposure, UV light is tenacious. Even in total darkness, a small amount of UV radiation is getting through, busily eroding the charge state of your EPROMs. With EPROMs, bitrot really is only a matter of time. But if you dump the EPROM bits to a file before the game goes bad, you can always yank the EPROM, zap it to a blank state with an EPROM Eraser, reprogram the 1's and 0's of the game from your .bin file, and the game should be refreshed and good as new.

 

 

Ben

[CPUWIZ]

Every time I read this EPROM bit-rot stuff, my stomach turns. To this date nobody has explained to me why most of the "dead" games I have come accross had mask ROM's inside and not EPROM's.

[Zeus]

Thanks for all these great answers. Being a person who is not educated in electronic engineering, but can understand the princibles if explained properly, I am getting a better understanding of how these mysterious cartidges work. The bit about the Activision contacts wearing out really hit home as these are the buggers I have the most trouble with. On thing, PCB's? Maybe I'm mistaken but isn't that part of the "dirty dozen" of banned chemicals?

[+wavemotion]

Every time I read this EPROM bit-rot stuff, my stomach turns. To this date nobody has explained to me why most of the "dead" games I have come accross had mask ROM's inside and not EPROM's.    

 

Two reasons I can think of... First off - maskable roms are not subject to bit migration (as EPROMS are), but are subject to simple static discharge, etc. as I mentioned in my post above. Couple this with the fact that far (FAR!) more carts use maskable ROMs rather than EPROMS gives you a much higher chance of finding a dead cart with a maskable ROM than a dead cart with an EPROM.

[Pitfall Harry]

Every time I read this EPROM bit-rot stuff, my stomach turns. To this date nobody has explained to me why most of the "dead" games I have come accross had mask ROM's inside and not EPROM's.    

 

Actually, llabnip hit upon a possible explanation. You can zap a ROM with 10,000 volts of static electricity simply by touching the cartridge contacts after shuffling your feet across a carpet. ROMs hate that.

 

 

Ben

[CPUWIZ]

The static discharge theory does make some sense, I need to try that.

 

@llabnip: I presume you mean EPROM's not EEPROM's.

[Pitfall Harry]

One thing, PCB's?  Maybe I'm mistaken but isn't that part of the "dirty dozen" of banned chemicals?

 

It stands for Printed Circuit Board. It's the plastic hoo-ha, usually green, with the shiny lines painted on it that lead from the ROM chip to the metal cartridge contacts.

 

 

Ben

[CPUWIZ]

It's the plastic hoo-ha, usually green, with the shiny lines painted on it

 

 

Sorry Ben but that was funny.

[+wavemotion]

The static discharge theory does make some sense, I need to try that.  

 

@llabnip: I presume you mean EPROM's not EEPROM's.  

Heh! Yep. I tend to get carried away with my E's. Those EPROMS used for Atari carts are not electrically erasable. I'll edit my post to avoid confusion!

[CPUWIZ]

One or two of the copy-carts actually do use EEPROM's but that's the only ones I know of.

[Nukey Shay]

This question comes up repeatedly...but there are still-functioning computer chips in other electronic gadgets that predate the Atari system and carts. I'd imagine they'd fail first before the "en masse" cartridge bit-rot.

[Pixellated Ghost]

I have a Tektronix 7603 oscilloscope mainframe from 1970 that has a character rom to generate the onscreen display for the switch settings. Still works fine, and it's definitely older than the Atari stuff.

[Shannon]

hehe... I'd probably get brain rot before my carts get bitrot.