I suspect that I don't really understand your question, but maybe the following information might help. For both of the PDP-11 emulators that I have used, Ersatz-11 and SimH, the disk image for an MFM hard drive is just a file in the hard drive under the operating system under which either Ersatz-11 pr SimH is being run. In my case, that is usually Windows 98SE although on a few occasions I have also used the 32-bit Windows XP. In addition, the original MFM DEC hard drive on which any of those disk images were based were totally independent of which DEC controller, RQDX1, RQDX2 or RQDX3, was actually used. And while the emulator might provide information which suggests that an RQDX3 is being used, the actual disk image on the hard drive would still be the same. On the other hand, I I have never tried to run ZRQCH0 under either emulator, so there might just be some aspects that I am not aware of. But to support my experience, if I have an RK05 disk image on the same hard drive (of 4800 blocks), I can also use that identical file as a disk image for the MFM emulator for both Ersatz-11 or SimH as if it was connected to an RQDX3 in the DEC hardware world EXCEPT that, of course, that disk image would then appear as a very small MSCP device of just 4800 blocks as a DU device under the Ersatz-11 or SimH emulator. I am not sure if I explained myself correctly or sufficiently. I am just trying to say that, in my experience, a disk image of an MFM drive in the DEC PDP-11 world (specified since you mention ZRQCH0 which run on a PDP-11) on the hard drive for use under an emulator, such as Ersatz-11 or SimH, is identical to most other disk images for any other DEC, in particular for those disk images which don't have extra data to handle the disk drive blocks. That means that there are some extra blocks for RL01 / RL02 disk images, but not for many others and, in my experience, that has included DEC MFM hard drives. I hope that the above information is helpful. On the other hand, Dave Gesswein's disk emulator may handle disk images quite differently and require extra blocks such as what an RQDX3 requires and which are probably different from what an RQDX2 uses. In that case, I don't know how you might create the disk image that Dave Gesswein's emulator requires. Jerome Fine