This request is actually more than on topic since the software in question was written in 1995. Specifically, John Wilson wrote HD.MAC in 1995 as a temporary substitute for DU(X).SYS to use large (up to 32 MB) disk drives under Ersatz-11. Being a bit of an RT-11 nut (OK a lot of an RT-11 nut, addict), I finally enhanced HDX.SYS to use 22 bit addresses under the Qbus so that I could replace VMX.SYS after I noticed that using HDX.SYS was so much faster than both VMX.SYS (3 times as fast) and DUX.SYS (twice as fast). PLUS, my minimum version of the LOADed code for HDX.SYS is smaller than VMX.SYS, supports a full 65536 block RT-11 partition (sort of obvious vs less than 8192 blocks for VM: on the PDP-11) and also supports the commands: SET HD: NAME (allows an RT-11 user to COPY HD.SYS VM.SYS) SET HD: UNIT=nn (n = 0 to15) (allows the RT-11 user to specify the Ersatz-11 unit) SET HD: [NO]WRITE (allows the RT-11 user to make the disk RONLY) In addition, I have written code which executes at the user level which, under Ersatz-11, avoids the overhead associated with an EMT request and is twice as fast again as using the HDX.SYS device driver. Whereas: COPY/DEVICE/NOQUERY DU0: DU1: takes over 2 seconds, COPY/DEVICE/NOQUERY HD0: HD1: takes just about 1 second and my user subroutines take about 0.5 seconds to copy the same 32 MB RT-11 partition. Compare that with about 5 minutes for an RD53 to RD53 copy and about 4 minutes for an ESDI to ESDI copy (using either Maxtor or Hitachi drives) on a PDP-11/83. The comparison figures are for a 750 MHz Pentium III. I imagine that a 3+ GH Pentium 4 will be about 4 times as fast, maybe even faster using SATA 2 hard drives of (1 TB?). Well, no good effort goes unpunished and one thing led to another. I am testing other versions including support for 64 units under RT-11 and I have a solution looking for a problem. I know that a few people have discussed a Qbus controller for the PDP-11 to use the current large disk drives. Well, MSCP emulation might be the final goal, however, I would be VERY pleased to support the HD(X).SYS code for anyone who might want to develop the hardware to interface this almost trivial example of an interface to the PDP-11 which uses 8 IOPAGE registers as detailed by John Wilson in his hobby version of E11 in the source file HD.MAC, although there are 2 essential details omitted in the documentation concerning 22 bit Qbus operation and size requests. The key point is that John Wilson's interface (based on a Russian idea which used only 4 IOPAGE registers) is a simple as any concept might be needing only the byte count, block number and user buffer address for each read or write request. Finally, I will also suggest to Bob Supnik or anyone else who may be interested that SIMH might also make use of HD(X).SYS since the interface should be just as efficient under that emulator as Ersatz-11. Does anyone reading this agree and if so, is Bob Supnik the best person to make this suggestion to? Does anyone reading this have both the interest and the ability to write the interface code for SIMH to handle an HD: type of disk drive? Can you suggest who might be interested or have that ability. For myself, while I also use SIMH, it lacks two essential features: (a) Built in VT100 emulation (b) Is only about 1/10 the speed of Ersatz-11 Can anyone help with a contact address for Bob Supnik and anyone else who may wish to consider my request? Sincerely yours, Jerome Fine