NorthStar uses a completely different format. The PC 765 FDC is very limited in the formats it is capable if reading. Basically It needs to see standard IBM 3740 single-density headers, or IBM system 34 double-density headers. It does support other sector sizes for those formats (IBM specs 128 byte SD and 256 byte DD sectors only iirc). The 765 DOES NOT have a "raw track" read or write capability - therefore, any diskette which does not have IBM format sector headers will be unreadable (the controller will just never find a sector). Also, the N* disks are hard-sectored. This means that the controller needs to see the individual holes to know where each sector data starts. The PC disk controller has no means to aligning individual sector data to index holes, even if it could see the sector data. There is a trick you can do, based on the fact that the PC uses independant diskette drive selection logic from that built into the 765 - you can "flip" with a sector header indicating an big (like 8K) sector and put it in one drive, and your non-PC compatible format disk in the other. Turn on the motors to both drives, then begin reading the known formatted disk until the controllers indicates that it's found the header. Then "flip" to the other drive, and read the raw data as the body of the sector (it will appear to be bad as it will not have correct CRC etc.) I've never tried this with a NorthStar disk - there is still no way to align the data to the sector holes, but you may be able to detect the sector gaps and work it out that way. I just haven't found it worth the effort - Reading with a read system and transferring the disk content via serial is an easy alternative. Regards, Dave -- dave06a (at) Dave Dunfield dunfield (dot) Firmware development services & tools: www.dunfield.com com Collector of vintage computing equipment: http://www.classiccmp.org/dunfield/index.html

On Mon, 30 Jul 2007, Andrew Lynch wrote: no The 765 can only handle formats with WD/IBM sector headers. It does not have any sort of "raw read" mode. In addition, the 765 can not read anything that occurs too soon after an index pulse, which rules out virtually any hard sector formats. That is correct. The index pulse is easily circumvented, by masking off the signal. There are a few boards available that connect to the drive between the FDC and the drive, to be able to look at the flux transitions, including Matchpoint, Apple Turnover, CopyII Option board, and Catweasel. It is also possible to kludge such a flux transition connection with a parallel printer port, thereby using absolutely minimal hardware. It is also possible to confuse the hell out of a 765 by switching drives in the middle of a read, using no additional hardware. Howzbout building an ISA version of the N* disk controller board that directly controls a floppy drives. -- Grumpy Ol' Fred cisin at xenosoft.com