Xerox 820 system disks in Teledisk format?

These steps *may* not be necessary - ImageDisk has a /S(address) option to select a secondary controller - it does not however currently support use of a different IRQ or DMA (mainly because I have no controllers which allow me to change these so I would have no way to test that functionality). Since IMD talks directly to the floppy controller, it makes sense to remove other software which may try to communicate with the controller at the same time. If the compaticard software is well behaved it may not be necessary to remove it, but I don't know this. Actually, as far as BIOS is concerned, floppy drives are 0x00-0x7F and hard drive are 0x80-0xFF - check the INT 0x13 functions - there is a clear distinction between floppy and hard drives. Also BIOS does NOT know about DOS mappings - the above reference physical controllers and physical units in the order encountered by BIOS. The trouble is that many PC users don't know what a unit number is, and this means more questions for me. "in the beginning" ImageDisk only supported the two standard drives defined by IBM and calling them A and B made sense, BIOS setup program and many DISK utilities which work through BIOS do this all the time and people rarely get confused - on 99+% of systems with one controller and only 1 or 2 physical drives, DOS maps them to A and B and everything matches up. This is by far still the most common ImageDisk configuration. Then someone asked for support for a common extension which allows two more drives on a controller by making use of free bits in the control registers which line-up nicely with were two more drives "should be". - This made sense to me so I added it, although you have to either explicitly specify one of the extended drives or tell ImageDisk that you have 4 drives to be able to select it - it made sense (to me) to call these C and D. To be honest it never occured to me that someone would confuse this with DOS mappings - I've tried to be very clear that ImageDisk works with the physical disk controller and NOT though DOS or BIOS. ImageDisk cannot and never could perform direct or destructive operations to a hard drive. The help clarify this point, I've added the following section to the help file with links from the "Settings" drive selection and the command line drive selections: ------------------------------------------------------------------- ImageDisk works by directly accessing the floppy disk controller. It does NOT know or care about DOS "drive mappings". Drive letters A-D refer to the physical drive unit numbers 0-3 on the the floppy disk controller, NOT drives A-D as mapped by DOS. For most systems having two drives on the primary controller, drive A and B will happen refer to the same drives as DOS - a few floppy controllers support a non-standard extension allowing up to four drives, and on these C and D will refer to the additional drives. Drive C is *NOT* your hard drive. ------------------------------------------------------------------- TestFDC doesn't support 8" drives - it's not intended to test drives, it's intended to test FDC's (Floppy Disk Controllers) - to make it easy, it gets information about the drive from BIOS (and BIOS cannot report an 8" drive) - the idea is that you can test a PC before ever taking it apart (with standard drives) to determine if it's worth hauling home and using as a drive station. Either an 5.25" HD (best choice since it's the same RPM as 8") or a 3.5" HD drive will allow you to test the FDC capabilities at a 500khz data rate which is what you need to run 8" drives. I'm glad you got it working ... Hopefully it will prove useful to you, even though you may not agree with the particular path on which has evolved. Dave -- 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