Xerox 820 system disks in Teledisk format?

That would be the use of the term "why on earth" - typically used in the context of things thought to be unreasonable, and the mention of "restrict" which suggests that you believed this to be an artifical limitation. How about "Why does it only support drives A-D?" That would have gotten you a response detailing the standard floppy hardware for a PC ... I should also note that the PC only officially supports *2* drives (A and B) - which is what ImageDisk originally supported - someone in the list pointed out to me that several controllers extend this to support 4 drives using unused bits in the PC drive select/ motor-on register which "has room for" 4 drives in a logical extension. Seemed reasonable to me so I added support for this extension (there's a note in my docs that most controllers don't support 4 drives however). Sadly I've got more and more machines these days with hardware supporting only 1 floppy drive ... and couple which support none. I believe Chuck G. has already responded with an indication that he can help. ImageDisk does not know or care about "Drive Type" - it completely ignores the BIOS settings (and manipulate the FDC directly - not through BIOS). The factors which differentiate one type of drive from another are the rotational speed, data rate and number of sides/cylinders - Rotational speed is based on hardware and is largely transparent to the program (with the caveat that it affects the number of sectors that can be placed on media at a given data rate) - ImageDisk has many options to pick and translate data rates and sides/cylinders. In other words, ImageDisk does not "know" what type of drive you have, you do. - So you need to pick an appropriate settings to accomodate the drive and media you are using - yes, it requires the user to know more about what you are doing, but the upside is that ImageDisk can handle any type of drive/media that the PC controller can talk to (even formats that were never made but could theoretically exist). I've encounteded enough "weird stuff" over the years that I decided to make ImageDisk work to the limits of the PC floppy design, not physical/known drive types. I have placed a fair bit of detail in my documentation describing the various common drive types and parameters and how they are related. The good news is that in 99.9% of cases, you don't need to worry about it much - the Automatic settings of ImageDisk do a very good job of figuring out how to read whatever type of media is in whatever type of drive you have. Recreating a disk is only slightly more complex, the recording settings are included in the archive file - you need to pick single or double step (mainly to accomdate 40/80 track drives) and may need to set a data-rate translation if you are recreating the disk on a different type of drive than the one it was recorded with. This too is covered in my documentation. TESTFDC was designed as a tool to evaluate the abilities of a PC's FDC system - It looks at the BIOS settings to determine the data rate and speed of the drive (you can override this if you like), and thereafter talks to the drive directly (same code as ImageDisk). I envisioned that people would use this to evaluate a PC before they started attaching drives to it, so I did not go to the bother of making a special case for 8" drives which are not supported by (or configurable within) BIOS - The idea is that you test PCs with it's standard drives, then pick one which passes and turn it into an ImageDisk machine ... 3.5" HD or 5.25" HD drives will test the 500kbps data rate used by 8" drives ... if it passes the desired functionality with these drives you should be good to go. -- dave09 (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