
PDP-11/04 – Restoration - lelf
http://www.datormuseum.se/computers/digital-equipment-corporation/pdp-11-04
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nasalgoat
Anyone who calls themselves a hacker needs to read this to calibrate their
definition.

This guy - he's a hacker.

~~~
ChuckMcM
Technically he's a DEC field engineer :-) But this is one of the reasons I
really enjoy the older DEC gear, there is so much documentation on how it
works (or is supposed to) that you can debug it to the chip level.

~~~
al2o3cr
DEC field engineer? That's handy, my waffle maker is broken. ;)

~~~
angersock
Be careful stripping the wires...

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fleeno
I'm currently working on an 11/23 here:
[http://bensinclair.com/category/pdp-11](http://bensinclair.com/category/pdp-11)

It's not quite as involved as this 11/04, but still a lot of fun. I'm not
having much like right now though!

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jonatron
I should finish my PDP-11 simulator one day:
[http://i.imgur.com/6RuI41d.jpg](http://i.imgur.com/6RuI41d.jpg)

The javascript PDP-11 emulator is pretty cool and works a lot better than my
own: [http://pdp11.aiju.de/](http://pdp11.aiju.de/)

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johnohara
Ask any DEC Field Service Engineer for a wire-wrap tool and they all reached
for their back pockets. Used to amaze me to see them sitting on the floor, a
step-by-step guide next to them, wire-wrapping some field service change into
the backplane.

Plus the banter: "You done yet?" "Two more. Got a screwdriver?" "No. How 'bout
a rum and coke?" "What's this power switch do?" "Haha, very funny."

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lachness
It's cool seeing this technology being used. My dad had a PDP-11/23 in the his
basement along with three 5 MB RL01 hard disk drives and 256K RX01 8" floppy
disk drive to with it. Is there anything useful/interesting to do with this
technology today?

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aw3c2
Warning, 40 megabytes of images.

If the author reads this, consider turning those photograph PNGs into JPEG.
There is no reason not to. Also resize them so they are not resized by the
browser but shown 1:1.

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hcarvalhoalves
> The CPU has no crystal to provide clocking, instead DEC used a delay line in
> a feedback loop.

Were oscillators back then expensive, unreliable, or it's another reason for
not using one?

~~~
VLM
No, but fooling around with the delay line is one way to implement single-step
or really slow step.

So either your next clock pulse is when a humanoid hits a button or when a
delay line times out.

Can't just gate in a clock using a "AND" because of jitter and syncing is more
trouble than its worth.

I never worked on this model so this is just semi-educated guess.

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WalterBright
Makes me sorry I had gotten rid of my LSI-11.

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pbrettb
Very cool! I started thinking in Octal again a bit while reading this...

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kjs3
Reminds me I need to get back to working on my VAX-11/730\. Nethack isn't
going to play itself...

~~~
ch_123
I don't know about the 730, but the 780 had a PDP-11 (/03 I think?) in the
cabinet which was in charge of the system console, and bootstrapping the VAX
processor with code from an 8" floppy disk.

Funny how their (then) new system needed its predecessor to get it up and
running...

~~~
Sanddancer
That's actually pretty common in larger systems. You don't want your big,
expensive machine bogged down with all the simple, stupid housekeeping stuff,
so most big iron machines have a frontend processor of some sort to handle
that. The DECs used a PDP/11 or an Intel 8080, depending on model, IBM tended
to use PCs or Thinkpads running special versions of OS/2, etc.

~~~
ams6110
Even a modern mainframe such as a Cray requires a management computer to get
it started. In this case of a Cray today it's a generic PC.

