Q-bus to CF [was: IOmega]

Jerome H. Fine jhfinedp3k at compsys.to
Fri Feb 29 16:02:32 CST 2008

 >Sridhar Ayengar wrote:

>> Bitsavers has AA-L619A-TK_MSCP_BasicDiscFnsV1.2_Apr82.pdf, 
>> AA-L620A-TK_StorageSysDiags_1982.pdf and 
>> AA-L621A-TK_UnibusPortDescription_1982.pdf at 
>> http://www.bitsavers.org/pdf/dec/disc/uda50/
>> I'm not sure if these are the scans I did five years ago (the file 
>> dates are later) but they're the docs you'd need.
> Excellent.  Thank you.  I'll see if I can give this a shot.
> Peace...  Sridhar

Jerome Fine replies:

I am not sure if this suggestion is easier or even useful.

>From what I gather of looking at the MSCP protocol from
the DU(X).SYS MSCP device driver in RT-11, there may
be an easier implementation that is just as useful.

John Wilson set up an interface for an HD(X).SYS device
driver under Ersatz-11 in order to provide variable
sized devices until the MSCP emulation had been coded.

While John's version of HD: needs a bit of modification
to work well with mapped monitors, it is still only for
RT-11.  On the other hand, for the past 6 months, I have
been adding additional features which include being able
to handle full 22 bit Qbus / Unibus interface for mapped

The real HD: advantage is the simplicity of the interface.
While there are 8 I/O registers, setting them up when
interrupts are not used takes less than 20 PDP-11 instructions
including the 22 bit address.  If you look at the hobby
version of E11, John includes the code for HD(X).SYS for
RT-11, although as I mentioned some changes are needed for
mapped monitors when the user buffer is above 1/4 MByte.

If anyone ever produces a Qbus / IDE (or any other PC
current drive) controller, I will gladly enhance the HD(X).SYS
device driver for RT-11 to use a DU(X).SYS translation
type table.

Sincerely yours,

Jerome Fine
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