| SYSTEM OVERVIEW | 11/55 |
This page shows the PDP-11/55 system. The picture shows the machine as it was in dry storage for many years. Above the processor is an
open reel tape drive of Cypher, model 100, installed. A Post It on the door of the tape drive says "Cypher 100, complete, not functioning".
A Post It on top of the H960 racks says "11/55 processor with 28 kW fast MOS memory". I will remove the Cypher tape drive, because I also
got a TU45 which is so much cooler (and also 'original' D|I|G|I|T|A|L !
The PDP-11/55 was the most powerful PDP-11 to date and was introduced in 1971.
The PDP-11/55 was an excellent computational tool for large multi-user, multi-task installations. Through memory management, memory could
be expanded to 128K, which included a combination of bipolar and MOS memory. Other features included a greatly expanded floating point
processor.
In many aspects, the PDP-11/55 looks similar to the PDP-11/70 which was introduced in February 1975. The PDP-11/70 added, among others,
a larger memory space (up to 4M) and cache memory. It is often said that the PDP-11/70 was the fastest PDP-11 when it comes to data
throughput (due to its four Massbus interfaces), and the PDP-11/55 was the fastest PDP-11 when it comes to execute calculations, as the
11/55 is optimised for processing speed on scientific workloads. The PDP-11/55 was used, for example, in air plane simulators.
The PDP-11/55 (KB11-D) uses the modified CPU of the PDP-11/70. The cache memory of the 11/70 was removed and instead the memory of the
11/55 is the faster bipolar memory. The 11/55 also has the kernel/supervisor/user operating modes as on the 11/70, but the 11/55 only
has an 18-bit addressing range. The 11/55 is the fastest of the PDP-11 CPU's when measured by the cycle times.
Raymond remembered that he saw my website a few years ago, and especially the "making of my museum space". He told me in an email (mid september 2007) that he always had planned to do something similar, but as time moved on, that his interest had shifted to other things. He had the feeling that I was as "DEC-minded" as he was years ago. His collection used valuable space for which Raymond had other purposes in mind. Finally, as he wrote me, he had decided that the day that he would make a "museum" of his collection would never arrive. It was then, that Raymond sent me an e-mail, asking if I was interested in his collection. He wrote a long (not complete!) list in his e-mail, which made me scratch my forehead.
Oh yes! I was certainly interested! I would almost immediately jump into my car to drive up to Uithoorn, but I would need a truck to move all this great stuff ... There was just one "minor" problem. How can I tell this to my wife in such a gentle way that she will not be against this undertaking? Here is the list that Raymond e-mailed me, and you will understand why my wife could be a major "factor" ...
That is not the complete list! Raymond also has several non-DEC printers in his collection. It was already clear to me that I could never
keep that complete collection without risking divorce ... I wrote Raymond that I would be very happy to take a part of his
collection, if that would be OK. Raymond excused that he had changed his mind and would like to keep the 11/40 and the 11/60, and asked if
I would still be interested ...
Yes of course! I already had an 11/40 and a "modified" 11/60 in my collection so I was sort-of glad
that he wanted to keep the 11/40 and 11/60! Raymond also wrote that the stuff was not used in many years, so the "usual" was to be expected
like the polyurethane capstan rollers of tape drives that went gooy, electrolytic capacitors that might require reforming, etc.
We planned a date, and I hired a truck with a hydraulic tailgate. Lukily, Raymond's collection was on the first floor. Using some shelves,
everything was easily rolled into the truck. I had forgotten to take my camery with me, and Raymond had not thought of his camera either.
I promised to take a few pictures while unloading at home ... so they can also be shown here
 [ 794 x 508 , 59 kb ] Start unloading, ropes partly loosened, and smaller parts like the TM02 are already unloaded. In the front you can see the DECwriter II and DECprinter I, the rear side of the RM03 and (partly) the SYSTIME tape drive. |
 [ 808 x 503 , 87 kb ]
I had to move things around, so here you can see the TM02 tape formatter in the front and the second |
 [ 734 x 527 , 73 kb ] The small goodies and two DECprinter I's and the DECwriter II are unloaded. The RM03 is turned, ready to be unloaded. Finally a clear view on the SYSTIME "SYSTAPE II" in its cabinet ... |
 [ 719 x 547 , 74 kb ] Moving on to the stuff in the middle of the floor. Two nice RK07 disk drives are ready to be unloaded. Behind them are four H960 racks waiting to be unloaded too! |
 [ 637 x 543 , 78 kb ] Finally getting to the "tall guys" in the rear. You can see the TU10, the PDP-11/45 and the TU45, all in their H960 rack. Hidden in the rear left corner is the PDP-11/55 ... |
 [ 639 x 527 , 73 kb ]
The TU10 and one other H960 with communication hardware is unloaded. |
I knew I would be taking way to much back home, but I agreed with Raymond that I would do the best to find a good home for everything, be
it in my museum or in the collection of somebody else. "That would be fine", said Raymond, "I'd love to receive an e-mail from the persons
where bits of my collection will find a good home".
Status now (end 2007) is that the PDP-11/45 and a DECprinter I found a warm place in Edward's collection, and the RT11 micro fiche set is,
thanks to Zane, in the computer part of the Library of the
Conner-Bishop Historical Resource Center. Edward also wants the TU10, but with
a PDP-11/45 in an H960 rack and a DECprinter I in the back, there was no room left for an other H960 rack in his car ... he will pick up
the TU10 on his next visit. The other DECprinter I and the DECwriter II were picked up by Bert Thomas.
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