jnc at mercury.lcs.mit.edu
Mon Jan 22 18:08:14 CST 2018
> From: Grant Taylor
> What makes the copies of papers printed on them special?
Well, the Dover was the first device (that I know of) that could print _very_
high-quality graphical/multi-font output, and on ordinary paper. It was also
pretty darned fast - a couple of seconds per sheet, IIRC. The whole package
just blew us all away (I was a MIT when we got ours).
There was a prior device (from quite a few years before) called a 'Xerox
Graphics Printer', but i) IIRC it printed on thermal paper (think
poor-quality thermal fax paper); ii) the resolution was nothing like as high
as that of the Dover (which was, IIRC, in the 100's of DPIs - which it needed
to produce the very-high quality printout with type-faces), and iii) it was
What they did with the Dover was take a high-end Xerox copier (one of the
things the size of a couple of desks),and rip out the optical front end
(which copied an image of the page being copied, onto the drum), and replaced
it with a scanning laser that was fed an amplitude-controlling bit-stream
from an interface card in the Alto.
>> That's the 'original' Ethernet; PARC did the 3Mbit one first, and the
>> 10 Mbit one came along quite a few years later.
> I assume this has something to do with the Digital / Intel / Xerox as
> in the DIX connector.
Right, a couple of years later Xerox, DEC and Intel did a consortium to make
Ethernet widely available, and produced the 10Mbit version. Technically, it
was little different from the 3MBit version. The low-level packet format was
different (because of the higher speed, and larger maximum size), and the
addresses used the later PARC thinking (UID's for interfaces), but those were
not major changes.
>> I'm trying to remember what kind of cable it used
> That sounds like typical Radio Grade cable.
Yeah, I just found a piece, I'll put up a photo.
> I'm not quite sure what you mean by "solid like CATV".
The CATV that used a heavy foil ground layer.
> That sounds like a description of what I've heard called a "Vampire
> Tap". My understanding is that's the poor way to connect to (what is
> effectively) the Ethernet bus.
Vampire taps worked fine on 3MB Ethernet. As the speeds went up, less so.
> I suspect that Wikipedia's article on 10Base5 has some decent pictures:
Nothing of the 3MB, and it doesn't show how the clamp-on connector and
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