Imaging floppy disks

There are several ways to create images from floppy disks, and this page describes some I have deployed.

Here some ways to categorize floppies and the data written on them.

Floppy sizes:

Floppy sectoring

Floppy encoding

Here some ways of reading floppies

Catweasel 1 Catweasel 1 ISA card The original Catweasel card was one of the first to use an FPGA based sampler to read data from a disk. A clock measures the time between flux transitions. The values are read by a program and analysed. The clock can be 7.083MHz, 14.166MHz, 28.322MHz. This is enough for most non High-Density floppies.
Nowadays ISA slot based machines are getting rare. BTW, there is a Catweasel MK2, but it has a Zorro connector, only found in some Amiga computers.
Catweasel MK4 (+) Catweasel 4 PCI card The Catweasel MK3 and MK4 were developed to allow hardware assisted emulation of the Commodore 64 and similar machines on a modern PC. You can connect original C64 joysticks and there are sockets for real C64 SID-chips. The clock can be 14.166MHz, 28.322MHz, 56,644MHz. The picture shows a Catweasel MK4+.
There are several packages interfacing with the PC based Catweasel cards:
DiscFerret DiscFerret Board The DiscFerret uses the same concept of the Catweasels but uses USB as interface to a host computer. The encoding of timing data for the flux transitions is even identical. The clock rates are different; 25 MHz, 50 MHz and 100 MHz. This makes it possible to read MFM and RRL encoded harddisks with a ST-412 or ST-506 interface.
Software for the DiscFerret is limited to a raw data dumper (Magpie) and an analysis program (Merlin) for this data. There are several initiatives for supporting other formats, one being my conversion for FM/MFM encoded disks.

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Last updated: 2012-03-03

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