FDC Gap Length?

Hi Guys, I've been doing a bit more work on my replacement for TeleDisk, and I have it working quite nicely, however I do have one area that I could some help with... The 765 FDC requires two "Gap Length" values, one for formatting (total gap between sectors), and one for writing... I have been unable to find any information about calculating these values from arbitrary sectors/track, encoding and transfer rate. All of the documents I have found simply give a table of suggested values for common disk formats, but give no hint as to how to calculate them for uncommon or arbritary formats. (for example, the fairly common 9x512 format is not included in the table). Currently, I am using the values from the table, and some "guesses" for values for some other formats which I have tried, however I do not know how to derive the correct value for these items. A couple hours on Google turned up numerous articals, ALL of which either: a) use a single fixed value b) use the NEC table c) call then "magic" numbers or d) say they can't provide more information on how to select GPL due to lack of information. With the 765, I cannot determine the gap length used on the original disk, so the best I can do is to try and determine a suitable gap length when formatting based on the # sectors, sector size, encoding method, transfer rate and drive type.... Can anyone provide any clues? Regards, Dave -- dave04a (at) Dave Dunfield dunfield (dot) Firmware development services & tools: www.dunfield.com com Collector of vintage computing equipment: http://www.parse.com/~ddunfield/museum/index.html