WinUAE

[gizmomelb]

Hi Toni,

a quick question for you if I may please - how does WinUAE 'emulate' the Amiga floppy drive?

Does it decode an ADF/DMS floppy image to memory and then the MFM decoded image can be accessed by the Amiga floppy controller and the floppy emulator circuit just works off set timers etc. to output the data at the rate which the floppy controller chips expect?

or

Does it actually fully emulate the circuit of a floppy drive?


Likewise for IPF images, are the IPF images unpacked as MFM data to an area of memory and then known timers etc. are used to emulate what a real floppy drive would report back to the floppy controller chips?

or is there a full (circuit level?) emulated floppy drive which reports back IPF disk errors etc.?

C/C++ code means next to nothing to me, but I'll try and work it out from the WinUAE sourcecode, I just thought it might be lazier and faster for me to ask the author

Many thanks,
Gizmomelb

[Toni Wilen]

ADFs/IPF/whatever are converted to raw data + separate buffer for possible timing data (IPFs only)

Disk controller emulation is normally called once per horizontal line (DMA) or when needed (CPU accesses DSKBYTR or any other disk-related register)

This also includes disk drive emulation (disk rotation position/motor status for example). Controller and drive aren't really separated in emulation code.

Internally emulation is "cycle-exact", one bit is copied from "disk drive" to internal register, dsksync checked (if enabled), DMA to RAM (if full 16-bit of data ready) etc.. Turbo-mode skips this part.

Hope this helps.