flash (or ide) storage for unibus 11?

Jerry Weiss jsw at ieee.org
Thu Nov 26 01:27:39 CST 2015

> On Nov 25, 2015, at 10:41 PM, Jerome H. Fine <jhfinedp3k at compsys.to> wrote:
> >Johnny Billquist wrote:
> ……
> For example, the DSD 880/30 (from Data Systems Design of course) emulates
> 3  RL02 disk drives using a single internal (non-removable) hard drive.  The box
> also holds a single RX03 floppy disk drive (8" floppy disk drive which supports
> using single-sided media specified by DEC as an RX02 floppy in addition to
> media which have the same physical interface, but which are double-sided).
> For a Qbus system, the dual module controller was the interface to both the
> three RL02 hard drives and the single RX03 floppy drive.  I don't know if
> DSD also made a separate controller for the Unibus for the DSD 880/30.
> With regard to the address support by the controller for the Qbus, the floppy
> drive definitely supported only an 18-bit address.  That 18-bit ONLY support
> by DSD was identical to the 18-bit support that DEC provided for its Qbus
> controller for the RX02, so both DEC and DSD needed a bounce buffer
> managed by software to support the RX02 floppy disk for systems with more
> than 256 KB of physical memory.
> As for DSD support for the RL02 for a 22-bit buffer address, a quick look
> at the DSD manual was not able to say one way or the other.  However,
> it seems more likely the the DSD controller for the RL02 supported ONLY
> an 18-bit address.  I have all the DSD hardware, but it is not operational
> at this point.  If anyone else has experience with the DSD controller for
> the emulated RL02, let us know if there was 22-bit address support for
> its emulated RL02 drive.
> Jerome Fine

Confirming that the original DSD 880 only had support for 18 bits DMA.   There are only 2 bits
in the CS register for extended addressing. I doubled checked the RT-11 handlers I had.  
There was  a Unibus controller for the original 7.8Mbyte RL02 reduced drive.  
Google 040018-01 DSD 880 Users Manual May81

The Sigma SDC RXV31 controller supported 22 bit DMA. 
See 400255-C SDC-RXV31 Floppy Ctrl Man Aug86

I used both, but double sided compatibility between the two products was
occasionally spotty.  Never did determine if it was a controller, floppy drive or media

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