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.



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.