🚀 go-pugleaf

In article <ROCKER.91Jun21192228@bucsf.bu.edu>, rocker@bucsf.bu.edu (The Long Haired One) writes:
> 
> These are probably a very simple questions. I just don't know the answers.
> I noticed that Pdp11's come in 2 types - qbus and unibus. Do the numbers
> of the machines like pdp-11/23 and pdp-11/24 relate to which is which type?

  Yup. In general, the 11/x3's are Q-bus: the 11-03/23/53/73/83/93 systems.
Unibus model numbers wander all over the place 8-). There are also some sys-
tems that are neither Unibus nor Q-bus; the PRO series comes to mind...

> And can someone tell me the differences between qbus-ing and unibuses, as
> to which is possibly better or what drawbacks they might hold.

  Q-bus is a somewhat newer system which uses multiplexed address and data
lines; the Unibus has seperate address and data buses. There are also other
differences, but that is the major technical one. Unibus systems tend to be
larger and more power-hungry. Recent advances (in geological terms) such as
block mode DMA and the PMI have made the Q-bus almost as fast as, and in
many cases, faster than, the Unibus.

  DEC no longer makes Unibus VAXen; they still make Q-bus ones. PDP-11's are
available in both configurations, although the current Unibus ones are actu-
ally Q-bus systems with a Unibus adapter.

	Terry Kennedy		Operations Manager, Academic Computing
	terry@spcvxa.bitnet	St. Peter's College, US
	terry@spcvxa.spc.edu	(201) 915-9381