PDP-11/20, was Re: ebay question

From: Paul Koning <pkoning_at_equallogic.com>
Date: Thu Feb 26 09:10:21 2004

>>>>> "Ethan" == Ethan Dicks <dickset_at_amanda.spole.gov> writes:

 Ethan> On Thu, Feb 26, 2004 at 08:23:46AM -0500, Robert Krten wrote:
>> William Maddox sez...
>> >
>> > > PS. There is a NICE PDP-11 waiting to sold at VCM.
>> >
>> > If you compare the picture of this machine with with the 11/20
>> on > Guy Sotomayer's site, the front panel of the machine on VCM
>> looks > like it has been (inexpertly) modified...
>> >
>> > Here is a picture of what I think a PDP-11/20 is supposed to
>> look like, > with a smooth front panel surface like the PDP-8/L of
>> similar vintage:
>> >
>> > http://www.shiresoft.com/pdp-11/inventory.html
>> Well... other 11/20's look a little different :-) :-)
>> http://www.parse.com/~museum/pdp11/index.html

 Ethan> Ruggedized machines aside, _my_ 11/20 looks like the one
 Ethan> depicted at shiresoft.com... smooth panel (with incandescent
 Ethan> bulbs behind).

Correct. The same goes for other PDP11 models; the smooth panel with
lights behind the translucent material is a common feature across the

Remember that the 11/20 came out in 1971. I'm not sure LEDs even
existed that long ago, and they certainly weren't common as lamp
replacements. I no longer remember when I first saw LEDs in PDP11
consoles -- perhaps the 11/70. Some vague memory says that their
lights displays looked red rather than yellow, which would fit.

Digging... the schematics in the pdp11 directory at www.bitsavers.org
support this: the 11/45 console schematics show lamps, the 11/70
console schematics show LEDs. The 11/20 console manual (KY11 manual)
also discusses lamps and shows lamps in the schematic.

Received on Thu Feb 26 2004 - 09:10:21 GMT

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