It's done completely within the program logic of the CP/M BIOS. It is not relevant to how HxC or KF function. It's only important when adding files to or reading them from the NSI image. If you want to see the effect of it, find a section of text in the NSI image that extends further than one physical sector (512-bytes). If the continuation of that text happened to be on the same track, it will be found 5 sectors (2560 bytes) further in the image. This obviously does not apply if the data is continued on the next track.Jeff wrote: ↑Thu May 31, 2018 7:33 amHave you a KF dump showing this skew ?snhirsch wrote: ↑Wed May 30, 2018 9:59 pm And, when I dig a little deeper into the Northstar diskette layout, it turns out they have a logical sector skew of +5 - at least on CP/M formats. So, I was half-correct . The machine is indeed not fast enough to read contiguous sectors, but they handle it in the CP/M BIOS rather than through physical format. This is evident from the cpmtools 'diskdefs' used to access files in an NSI image:
Bottom line: Nothing you need to worry about unless you plan to add capability for extracting files from the NSI image. I mentioned it only to make the point that the computer was not able to read contiguous sectors. Logically staggering them allows enough time to read the next allocated sector of the file without waiting a full revolution. Every CP/M system I've ever encountered used a skew. My mistake was in assuming the Northstar applied a physical skew. We now know that isn't the case and that the skew is logically applied.
Have you made any progress on correcting the Northstar read errors?