Re: Tips for making Twiggy images

Sorry for this late post, I have been away.

>how much can you read talking to the floppy controller, and
>how much is really stored in the disk.

The floppy disk controller in the Lisa is not an opaque black box as it is in some computers, it is a 6504 microprocessor with code in EPROM, and the commented source code is available online.

It is even less opaque than the Mac, as the Lisa 1/2 don't have an IWM, they use a relatively simple state machine built from an off-the-shelf shift register, hex flip-flop, and 256 byte PROM, which performs the serial/parallel conversion and "bitslip FF" synchronization with the bitstream.

The GCR translation is done entirely by the 6504 as well.

As a result, there are no mysteries about the flux transitions on the disk, the 6504 code controls it all.

However, I have 1 rare twiggy disk (Lisa Basic disk 2) that has a crucial bad sector, and it could be that being able to read the flux transitions would make it practical to recreate that sector.

>Free, opensource, http://github.com/claunia/DiscImageChef

Thanks for that contribution!

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