[Simh] weird question about the VAX's DZ port

[Ethan Dicks]

On Fri, Mar 13, 2009 at 4:51 PM, Jason Stevens <neozeed at gmail.com> wrote:
> I found this site:
>
> http://anachronda.homeunix.com:8000/~rivie/cpm-vax/

Wow... that's strange and wierd.  I may have to try that on a real uVAX2000.

> And from vax780_defs.h:
>
> #define IOPAGEBASE      0x2013E000
> #define IOBA_DZ         (IOPAGEBASE + 000100)           /* DZ11 */
>
> which doesn't quite seem right... I'm guessing the 000100 is Octal,
> not Hex?

Yes.  In C, prefixing a number with a '0' makes it an octal number.

What's not clear to me is if a MicroVAX 2000 "DZ" is identical at the
register level to a DZ11 or not.  If they are, then it might work
unchanged.  If not, then there would need to be some work done on the
CP/M-68K image to grok Unibus gear.

Register compatible or not, the 11/780 (and other large-box VAXen)
have real busses with historical I/O locations (inherited from the
PDP-11 days) and such.  The MicroVAX2000 is a closed beastie with no
bus, so they assigned peripherals where it was convenient to, and
didn't have to worry about strict backwards compatibility.

-ethan