Simulated disk drive for RT-11?

[Tony Duell]

> 
> I have a device that plugs into a serial port on a PC and looks like a 
> disk drive to an Atari 800. Is there such a thing for RT-11? It seems 
> like it should be possible to write a disk driver that uses a serial 
> port and some sort of serial protocol to communicate with a PC and make 
> RT-11 think it is accessing a local disk drive. Has anyone done 

If you'll accept it emulating a tape drive, make it emulate the TU58. 
That has an asynchornous host interface (which is trivial to turn into 
RS232), and a fairly simple protocol which is documented in the user 
manual IIRC. The TU58 is a block-structured device, so it is pretty 
similar to a (very slow) disk to the software.

There must be an RT11 driver for it (DD.SYS?)

I think there used to be unix-based software to emulate a TU58 (so that a 
PDP11 conneccted to a serial port on the unix machine thought it had a 
TU58 connected). It must still be around somewhere.

> Another related question is what is the smallest QBus backplane mounted 
> in a box with a power supply that will support an 11/23 CPU (M8186), a 
> memory card (M8044) and a serial port/boot rom card (M8047) and maybe a 
> multi-port serial card (M8043)?

A BA11-V. It's tiny -- a dual-hight 4 slot backplane alongside a little 
PSU. I think it supports Q18 (which is what you need for the 11/23), but 
if not it should be trivial to wire-wrap. 

-tony