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PDP11/05 - Quick look and Teardown

Pretty cool - I noticed the control panel is much smaller than other PDP-11's - can you fully debug with it or is it a smaller more limited control panel?
 
I haven't used it (recently at least, if at all?), so I'm not completely sure.

But according to the manual (link below), memory contents can be examined and altered, and programs can be single stepped.
So I'd say it's a go for basic debugging, though without more advanced facilities like breakpoints.

https://www.vintagecomputer.net/digital/PDP11-05_BA11-K/DEC-11-H05SS-B-D.pdf

No front panel operation have things like breakpoints...
If you want a breakpoint, you insert your HALT where you want it.
 
My question is because usually the CP is taller and has a dial for selecting what is being displayed (so you can evaluate/see things like the registers/accumulator). That seems to be a very compact CP.
 
No front panel operation have things like breakpoints...

I wouldn't have thought so either, and mentioned it only because the question said "fully debug", and just in case such a beast actually existed.

My question is because usually the CP is taller and has a dial for selecting what is being displayed (so you can evaluate/see things like the registers/accumulator). That seems to be a very compact CP.

Some of the PDP11s have such a switch, I'm not sure if it's present on the majority of models (I suspect not). The /04 & /34 also have just a single display which show address or data depending on context. Some (/03) have no display at all.

I'm just playing with two PDP8s now. The PDP8/F has the switch, but the 8A is similar to the PDP11/04 & 34. Though it's possibly better than all of them, as it appears to have both address and data displays that are visible simultaneously, unlike any of the other PDPs I have.
Edit: The 8/F has a separate display for addresses, and the switch selects various data sources to show in the other display, so probably the best of all.
 
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That power supply is used in many DEC chassis. We spent a lot of time learning about and repairing one in a DW8-E chassis in a PDP-12. We had to Spice simulate the supply so we could understand how it works. The -15V switcher is very sensitive to the size of the electrolytic capacitors. The one in the PDP-12 has a 3000 uF capacitor, but we found that it would not work correctly with 3000 uF capacitance. Our testing and the simulations showed that it needed more than 3000 uF to work correctly. We are speculating that the +80%/-20% tolerance on the electrolytic almost guaranteed that a capacitor labeled 3000 uF would have more than 3000 uF capacitance and would work correctly.
 
Some of the PDP11s have such a switch, I'm not sure if it's present on the majority of models (I suspect not). The /04 & /34 also have just a single display which show address or data depending on context. Some (/03) have no display at all.

I'm just playing with two PDP8s now. The PDP8/F has the switch, but the 8A is similar to the PDP11/04 & 34. Though it's possibly better than all of them, as it appears to have both address and data displays that are visible simultaneously, unlike any of the other PDPs I have.
Edit: The 8/F has a separate display for addresses, and the switch selects various data sources to show in the other display, so probably the best of all.

Unless I remember wrong, the 11/34 is similar to the 8A, in that you actually select what is shown in the data section by manipulating the panel. So there is no rotary switch, but the same functionality is achieved through a different method. In the 8A you have a "DISP" button. So you press one key (they all have labels above telling that they select) and then DISP, and the data part will then display that kind of data. I think 0 is "AC", so 0 DISP will show the AC in the data display. Just as the rotary dial on the 8F set to AC shows the AC.

The 11/05 is a bit more limited on the front panel, but on the other hand is the CPU rather limited as well. But it can show both address and data on there, and you can examine and modify memory, as well as single step things, so it can pretty much do and show as much as any other front panel. But because of the shared lamps, it is a bit more context about it.
 
I have limited experience with all of these units, but most is with the 11/34 & 04, where I found the lack of simultaneous address & data display annoying, as I was often unsure of which address the data was associated with. It seems the 8/A panel is an improvement on those.

My home made micros back in the 1970s had both address & data displays, which I miss on my PDP11s.

My very first computer was an EDUC-8, an Electronics Australia magazine project, which was heavily based on the PDP8. It had LED displays for PC, MA, MB, AC, State & Instruction, so you could see everything. http://www.sworld.com.au/steven/educ-8/index.html

I wish I had kept the front panels from a couple of System/360s that I scrapped back in the 1980s - Now that was a front Panel!
 
Thanks for posting the video.

You have an interesting combination of memory boards in your system. I'm pretty sure the Plessey board is a stand-alone Unibus memory, meaning it has all the necessary addressing / driver circuits to operate the core, and thus doesn't require the G110 and G231 boards to function. I purchased one of these off ebay after I got my /05 (which came with an H216), but unfortunately the core in it was busted. Perhaps at one point your system had an H214/H215/H216 that died and was replaced by the Plessy.

Also, definitely no sign of those extra console connector wires in my system. I'm intrigued as to what they were trying to accomplish there.

--Jay
 
I'm pretty sure the Plessey board is a stand-alone Unibus memory, meaning it has all the necessary addressing / driver circuits to operate the core, and thus doesn't require the G110 and G231 boards to function.

Perhaps at one point your system had an H214/H215/H216 that died and was replaced by the Plessy.

Also, definitely no sign of those extra console connector wires in my system. I'm intrigued as to what they were trying to accomplish there.

Thanks, that's interesting.

I knew of the G110/H214/G231 combo, and wondered if that Plessey module was supposed to replace an H214, why did it have a whole lot of extra electronics that the H214 doesn't? And which looks a lot like the electronics on the G110/G231. So your suspicion that the Plessey board can run standalone seems plausible.

I do have at least one H214 around here somewhere (but it has a broken chip), so maybe it was all meant to be in there, for more memory.
Or as you surmise, maybe it just replaces the broken H214.
But then, there was an undamaged H214 also, so maybe not, but I gave it away long ago.

I also have another (different) Plessey module that seems to have been in a 4 slot Unibus extension.

It's also good to know that I can probably forget about those extraneous wires, and the UART TBMT bodge wire.
 
Nice machine!

I have also a Galway PDP11 in the small cabinet. But mine is called the PDP11/10.
It seems they have changed the cooling system over time. You have a ventilation grille
underneath the switches. My machine is closed an the front. In my machine the air is
pulled into the machine at the boards side and is blown out at the power supply side.

So the heat of the boards is actually blown over the power supply. Not the best solution I think... :dontgeti:

Is the airflow of both of your fans in the same direction like from the back to the front?
Or did they keep the airflow direction the same as my machine?

PDP11_10 01.jpg air flow.jpg

Regards, Roland
 
Nice machine!
... But mine is called the PDP11/10....
Is the airflow of both of your fans in the same direction like from the back to the front?

Thanks, I'm not sure what the difference is, but the manuals seem to lump the 11/05 & 11/10 together...

I haven't powered on my 11/05 recently (if ever?), and it's all in pieces anyway, pending new power supply caps.
Looking at the fans, I can't see an airflow direction arrow, but both of them have the stator/label side of the motor toward the outside.
So if say, the air comes in from the stator side (needs to be checked), they would be blowing onto the boards, and into the PSU.
HTH
 
It's just my observation but the solid cast metal fascia grille seemed to be only on the early 11/05 and 11/10, from late 1972 to early 1973.
This can be seen in the PDP-11/05/10/35/40 processor handbook photos on pages 4-74 and 6-24.
My s/n 151 machine has this style solid grille. It also has the cast-in pure white digital logo on the console frame, which along with the change to the plastic slotted grille went to the separate stuck-on magenta badge for the majority of 11/05 production.
Roland's machine shows both the early grille and the common badge style. I did some waterside decals for this badge a while ago.
 
Just correcting myself above, I really meant from 1972 to 1973 for the early grille and bezel, from the machines I've seen on eBay and elsewhere. Also the early bezel was painted black just on the strip directly underneath the switch paddles,as well as having the cast-in nameplate.
 
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