On Wed, Aug 29, 2018 at 4:17 PM Arthur Krewat <krewat@kilonet.net> wrote:

> LOL - very true, Clem. That was a shameless bit of self-promotion. From
> what I can tell, SIMH does not support a DH11. Yet.
>
Note I have not tried this .... but from the simh mailing list:

  * The UNIBUS DH11 and DHU11 had 16 lines per interface
  * The QBUS DHV11 had 8 lines per interface
  * The QBUS CXY08 was DHU/DHV compatible and had 8 lines
  * The QBUS CXA16  "    "   "    "   "    "   "  16 lines

*Supposely, the DHV11 works ..... its been on my >>round tuit<< list for a
while to verify!!!!*



>
> But when is an emulated interrupt a bad thing? Except for the idle loop
> that may or may not be optimized, the rest is balls-to-the-wall CPU bound
> anyway. And these days, even emulated, we're orders of magnitude faster
> than the original hardware.
>
Yeah, but since the 780 was slow on interrupt processing, why stress it any
more thsan you have too.



>
>
> http://simh.trailing-edge.narkive.com/Sc9HBFZU/multiple-telnet-ports-in-simh-to-rsts-e-9-6
>
> I recognize a familiar name in there ;)
>
Yeah a couple of them ;-)




>
> But yeah, when a DZ11 was blazing away at 19200 baud (I hacked the TOPS-10
> 6.03A we had at LIRICS to support it), it made the system crawl.
>
No doubt.   CMU and MIT had front ends that put the serial lines on
dedicated PDP-11s in front of the 10's - so the Tops (or ITS) only saw
canonicalized I/O and it made a huge difference for those systems.  By the
time Vaxen, I don't think DEC had yet realized what a problem the DZ was.
 The DH's issue was cost (and space) since it was implemented in MSI TTL
and took up a full 'PDP-11 System Unit' on the bus.  The DZ11 gave you 8
serial ports in a single PDP-11 slot, which was a huge win.
ᐧ