I found a couple of old floppy disks from the 90s, one of which had become unreadable. I have a load of other disks, mostly Amiga ones, so decided to preserve them.
The Greaseweazle is a USB floppy controller. It’s only 20 quid, and can read and write almost any format disk. 3.5″, 5.25″, 8″, almost anything. You have to supply your own floppy drive and cables. It can
read and write copy protected disks too, including original Amiga games.
I initially had a bit of trouble updating to the latest firmware, but sorted it out. There are two bits of software for reading and writing disks, the Greaseweazle’s own software and FluxEngine. They can both
make archival quality copies of disks, so I decided to just do every disk with both of them. I’ve had Greaseweazle crash a few times, but now it seems to have settled down. Archival disk images are about 40MB each.
They can also make “normal” disk images like .ADF for Amiga floppies. WinUAE supports it so you can use it as an Amiga floppy drive within the emulation, and actually load original Amiga games.
I am working through my disks now. Some of them are sounding a bit rough, so I’m glad I’m backing them up now. 3.5″ disks tend to be okay, older 5.25″ disks tend to rot or get mould on them. Some of the
disks are physically falling apart or damaged too. I take a few seconds to look them over and manually slide the cover over before inserting them in the drive, just in case. So far they all seems to be
okay though.
A bit of technical stuff. Normal floppy controllers read the disk bit by bit at a fixed speed, e.g. every 4 microseconds read a bit. The Greaseweazle instead records when the bits change from 0 to 1 or
vice-versa, with a very accurate timing system. That means any format can be read, it doesn’t matter what speed or density the original machine used. For archival quality backups you read each track 3
times, so it’s slower than normal. For making .ADF images it reads at normal speed.
The most common copy protection method on the Amiga was to use “weak” bits. The Amiga reads bits from the disk at regular intervals, but the floppy drive motor doesn’t maintain perfect speed so the RPM drifts up and down a bit on every rotation. Using a commercial disk duplicator it’s possible to have a bit that changes from 0 to 1 or vice versa right at the moment the Amiga is going to read it. Because the RPM fluctuates randomly, it’s also random if the Amiga reads a 0 or a 1. The game reads the track a few times and if it sees the bit randomly changing it knows it’s an original disk. The Amiga can’t write weak bits, so the disk can’t be copied without a very expensive commercial duplication machine… Or a Greaseweazle.