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Restoration of a PDP11/60

pbirkel said:
DEC FP11-E PDP11/60 Floating Point

Ouch!
Click to expand...
Damn that is pricey! Luckily the 11/60 has floating point integrated in the microcode, so you get the full FP instruction set on the base machine.
FP11-E is only needed if you want the highest performance solution (IIRC the FP11-E is the highest performing FP11 of all the PDP-11 FP11s).
 
So I'll mention a couple of things from my experience restoring a couple of PDP-11/40s.

Across two PDP-11/40 processor sets, I need to replace about 15 chips:
  • 74H50 x3
  • 74175 x2
  • 74174
  • 74153 x2
  • 74194
  • 74151
  • 7474
  • 7450
  • 7404
  • DEC 8815 (more or less a 7425)
Of those chips, none of them were unibus driver chips. I would recommend against attempting to debug the unibus by starting with the suspicion that a driver is at fault. The circuitry for generating the unbus timing/signals is very stateful. In my experience, it has been some state-keeping element that has died, for example, a 74175 or 7474. I don't know the design of the pdp-11/60, but in the case of the PDP-11/40 when doing a unibus transaction, the CPU clocking shuts off. Later, on the completion of the unibus transaction, the CPU is resumed asynchronously. In the case of the 11/40, when there is a serious unibus fault, the CPU will lock up and the system will be unresponsive and or malfunction in odd ways.

Put the unibone to the side for now, and get yourself a set of UniProbes. It's good to have one installed all the time in the system so you can watch the LEDs. They are good for spotting anomalies. But more importantly, it's a fantastic tool for connecting up a logic analyser; you won't need to connect up all the signals, you can get away with as few as 8 if you have to.

The next thing you need to try and figure out is if there is some kind of maintenance interface available on the system. You're not going to get far from its front console on its own. The 11/40 uses the KM11.


Doing some spread reading of the available documentation, you will need to find yourself a "DCS (Diagnostic Control Store) Module M7871 (KU116-BB)".
It's described here:
https://www.bitsavers.org/pdf/dec/pdp11/1160/EK-KD11K-TD-PRE_Jan78.pdf
And here is some of the docs:
 
ashlin4010 said:
Doing some spread reading of the available documentation, you will need to find yourself a "DCS (Diagnostic Control Store) Module M7871 (KU116-BB)".
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It is not quite easy to find an M7871, even not to find working standard boards. In the meantime I found some 11/60 CPU boards but they are also faulty ...
So if someone wants to get rid of 11/60 CPU boards, we are interested :)
 
The PDP-11/60 is a very complex system, but very structured in its design. Without debug tools, you will need to learn and understand the architecture to be able to build your own debug tools.
The architecture docs for the 11/60 are a little sparse (as far as I can tell), but I think there is enough info to work with.

I would recommend you study the schematics and docs. Using that info, build a simulation of the core elements. The goal is to understand how the system works; your simulation does not ever need to run.

This is what I did for my PDP-11/40; in the end, I never got the simulation running, I had enough understanding of the system from trying to build a simulation that I was able to move directly to component-level repairs.

Once you understand the architecture and have the right tools, you will find that you will be able to track down and fix most issues in a day.

I would say the PDP-11/60 is 2-3 times as complex as the 11/40, and getting my two CPU card sets fixed took about 11 months.
https://blog.tephra.me/tag/pdp-11/
 
ashlin4010 said:
Once you understand the architecture and have the right tools, you will find that you will be able to track down and fix most issues in a day.
Click to expand...
We decided to start with a Unibone:
T

Post in thread 'We've now also built one of those Unibones'

Hello, the boards look very clean, nice job.
I do want one Unibone at a reasonable price :)
I have a PDP11/05 that is sitting pretty on a garage shelf and patiently waiting for it.
I am in California, USA. Please DM me, as I don't have enough mojo to DM you (or anyone else).
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ashlin4010 said:
I would say the PDP-11/60 is 2-3 times as complex as the 11/40, and getting my two CPU card sets fixed took about 11 months.
Click to expand...
Time is not a problem :)
 
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