PDP-11/20 in Iowa (x3)

Paul Anderson useddec at gmail.com
Tue Mar 28 00:48:10 CDT 2017

If you are concerned about hex height boards or mos, you can always use a
BA11-KE expansion box.

On Mon, Mar 27, 2017 at 6:04 PM, Ethan Dicks via cctalk <
cctalk at classiccmp.org> wrote:

> On Mon, Mar 27, 2017 at 12:20 PM, Al Kossow via cctalk
> <cctalk at classiccmp.org> wrote:
> > On 3/27/17 7:37 AM, Systems Glitch via cctalk wrote:
> >>> I don't know of MOS memory appearing in 11/20s as built by DEC, but
> there's no reason against it.
> >
> > There were 3rd party cards, Monolithic Systems, for example.
> > The problem with the 11/20 is that hex wide cards don't fit, the fans
> overlap the unibus jumper area.
> > If you ever see hex-wide cards with a big notch in one end, they were
> designed to work in the 11/15 11/20
> Exactly.  There are plenty of hex-height cards with MOS memory for
> Unibus (I have several for the 11/04 and/or 11/34 of a suitable size)
> but they would fit in an external BA11-K or BA11-L w/DD11-DK, not the
> CPU's BA11 because of the fans.  That's why I was wondering if DEC
> ever made quad-height MOS modules for Unibus or if all DEC-supplied
> 11/20s and 11/15s had core and only core.
> -ethan

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