If we have told you that your game disk(s) have been modified or are copies, it means that a different drive has written some of the tracks, or the whole disk was written with a home computer respectively.
We can see when this happens as each mechanical drive has its own “fingerprint”, made by the “crackles and pops” unique to each one. Disk images made from commercially mastered disks have far less of these mechanical stutters due to the high quality equipment used.
The usual case here is that your disk(s) had been partially or fully written on your or a previous owners system. If the game seems original then it is probably because it was copied using a hardware device (Cyclone, etc). Hardware copied games are very easy to spot as they are normally very badly written due to the quality of the devices and the “analogue” way they are copied.
You may or may not have been aware of this, it certainly could have happened at any time. Factors involved here are things like who you bought it from, who you lent it to, basically somewhere down the line to the original purchase. We have even seen some copied originals that appear to have been copied in the shop. Perhaps this was to fix an otherwise broken disks, though it is strange since the shop could have returned it at no cost to them. However, the owners of these games swear that they have not touched it since purchase, so this can be the only logical conclusion.
- The game may store save points on the disk. This is a stupid thing to do by the developer, and unfortunately fairly common. Some games will not even work unless you write enable the disk! Yes, this does cause us headaches.
- The game may save high-score information to the original disk. This one in particular stopped us from releasing things like The Great Giana Sisters for years. In general, we do not know what the high-score table should be, and it is not an authentic until we find an unmodified one.
- You, or a previous owner may have at some point been infected with a virus, or just as damaging, a virus killer mis-identified the game code as a virus and tried to fix it.
- It could be caused by a faulty drive whose disk write-enable detection mechanism has been broken, though this should be pretty rare since the drive is more likely to think all disks are write protected than enabled.
- It could the fault of the operating system. For example, on the Commodore Amiga, there were versions of the “Workbench” that modified disks as soon as they were put in the drive write enabled, writing a “.info” file into every directory a user navigated to.
All of these reasons mean that you should always image disks with our tool and ensure there are no redumps needed, before testing if they work.
In all probability, the disks went bad at some time in the past and a previous owner “fixed” them by copying the game back over them with a crack, or even an original using a hardware copier.
As of writing, out of thousands upon thousands of disks (disks, not games) there are only six that we can confirm were actually released duplicated by either a home system or some early duplication equipment. Most of these games are very old and so the latter is more likely to be the case. On the Commodore Amiga, contrary to popular belief it is almost unheard of for a game to be duplicated on the system itself. This is because getting it duplicated professionally was actually cheaper than buying the blank floppy disks.
For example, we were starting to think that the game Lionheart was duplicated on Commodore Amiga’s, especially since the game has not any physical copy protection. Then, a huge number of copies imaged later we at last found a commercially duplicated version. The hint to this one was that no version imaged was duplicated with the same system - and hence we kept looking.
If we get multiple disk images of game disks written using the very same system, we know that was how they were duplicated. For example Fatal Heritage by Ego on the Commodore Amiga. Multiple copies of this game turned up that looked like it was copied on an Amiga, but all used the exact same duplication system. In this case we were helped by two facts. The first being that one copy came from the developer themselves, and the second is the fact that it had a type of protection that you cannot copy on an Amiga - even with a hardware mastering device.
Back to the point. We cannot release any games that are like this since it is likely not an authentic image from an original disk.
In the case of copies, we cannot verify they are unmodified because if the game was copied with a home system, how do we know it wasn’t changed before it was copied? Well, we can’t... Sure, we can tell if the copy was modified since some tracks will look like they have been written with a different machine, but if we were looking at a copy of a modified disk, we would never be able to tell.