Re: Did Commodore cheat with the quad density floppies?

On 04/01/2019 05:14, William Levak wrote:
> It's not more efficient. It's more accurate. In MFM, if you have a 
> long string of zeros, reading accuracy is limited by the accuracy of 
> your clock. GCR eliminates this problem.
>
Neither MFM or GCR can have "long strings of zeros", they were both 
invented to eliminate that particular problem.

MFM is less efficient because it requires 2 transitions per bit, while 
GCR needs less (depending on the particular encoding type, IIRC 
commodore used 8 to 10).

However MFM is more accurate because it guarantees there will only be 1 
zero transitions, GCR can have more.

This allows MFM to be clocked faster and still be reliable.