Fred Yaryan before PDP-7 with serial number 129
I recently met with Fred Yaryan, a former Boeing engineer, and Jeff Cailin, an engineer at Living Computers, to discuss their work on the PDP-7 restoration at Living Computers: Museum + Labs. PDP-7 (from Programmed Data Processor , "programmable data processor") was introduced by The Digital Equipment Corporation (DEC) in 1964.
In the early 1960s, the term “computer” was a synonym for huge and expensive cars, which were often difficult to understand. DEC chose the name PDP for its machine in order to avoid such negative connotations.
DEC found buyers for the PDP-7 nationwide, in particular at Bell's laboratories, the Pacific Northwest Coast National Laboratory and the Jet Propulsion Laboratory. PDP-7 was also popular at universities - in particular, it was sent to Oxford University, MIT, Helsinki University of Technology and Tokyo University.
Today, finding the PDP-7 in working condition is an extremely rare success. For many years it was believed that there were only four of them in the world. Of these, two were located outside the United States, one on restoration in Oslo, Norway, and the other in a private collection in Australia.
The third was in the storehouse of the Computer History Museum in Mountain View, California, and the fourth was in the Living Computers: Museum + Labs in Seattle.
The latter was originally installed in the Department of Nuclear Physics, University of Oregon. Having accepted the package, Professor Harlan Lefebvre and his laboratory for three years wrote the necessary software to carry out their research. Upon completion of this work, the system proved to be extremely reliable: over the next four decades, it worked for more than 60,000 hours and allowed 23 post-graduate students to receive a doctorate.
Before another car was discovered in the possession of Yaryan, the last PDP-7 was considered the only one in the world. Earyan with a smile recalls the first time he heard his story, the first time he got to the LCM + L museum.
“I went to the museum, and someone told me: 'Oh, this is the only working PDP-7.” And I replied: Well, actually, I have the same in the basement! ”
Yaryan, a graduate of the School of Electromechanics at the University of Washington, worked as an electrician at the Pacific Northwest Coast National Laboratory for several decades. He spent a significant part of his career at Boeing helping launch flight simulations to train astronauts in the Kent Space Center. During this time, he perfectly mastered various computing systems, including SDS 930s, Varian Data Machines and Tektronix.
It was a wide range of his knowledge that led Yaryana to the Boeing development center in 1973 to work there, as he himself says, on "work of a very technical kind - to repair computers here and there."
During this visit, he noticed the PDP-7 among the cars. Apparently, it was connected to the local SDS 940, and the whole system was designed to demonstrate the processed data.
He could not know that a few years later, in 1979, he would find the same PDP-7 in a surplus store for sale by Boeing. He often went there to buy wires or other things for his projects.
When he first asked the store about the PDP-7 for the first time, he was told that it was not for sale, because someone wanted to take it apart for parts, including a paper roll printing system. But on one of his next visits, he noticed that the computer was still standing there. He again turned to the sellers, and in the end was able to buy this system for $ 500, load it on his pickup truck and take it home.
PDP-7 settled in the basement of Yaryan, and after this move, the new owner encountered problems in the computer. He soon discovered the source of these problems. As he himself says: “The problem arose periodically. PDP-7 stood at Boeing for a very long time, and they could not find its cause. I debugged it with the old Tektronix 45 and found it - the terminator was in the wrong place. "
After making PDP-7 work, Yaryan wrote a program for him on BASIC on another computer, and then downloaded it to this one and confirmed that everything was working correctly. And from that moment 25 years passed before Yaryan first visited the LCM + L museum in March 2017.
After Yaryan talked to the guides during this visit and told them that he had a PDP-7 at home, the museum’s engineering team contacted him.
“At first we were skeptical of this information, since in the past we already had cases when people came to the museum and said that they had something like that, but in the end it turned out that it was either not something or something it’s completely non-working, ”said Stephen Jones, managing director of the museum. “But after talking with Fred during his first visit, we made sure that he had a complete, and possibly a working machine.”
On November 7, 2018, more than a year after this visit, several museum engineers, including Jeff Kailin, Cindy Moyu and Stephen Jones, arrived at Yaryan's house to take the PDP-7 out of his workshop and load it onto a pickup truck heading to the museum.
Soon, the team began working on loading the UNIX Version 0 operating system onto the machine. In doing so, they wanted to pay tribute to the fact that Ken Thompson wrote UNIX Version 0 on an old PDP-7 machine in Bell's laboratories in 1969. This year, UNIX celebrates its 50th anniversary, making the restoration project timely.
In addition to loading UNIX, engineers worked to add direct memory access and I / O interfaces to the PDP-7, which would allow data to be transferred to main memory.
This was done through a disk emulator JK09, connected to equipment made specifically for this computer in the Boeing laboratory. They added a device driver (probably the first new driver for UNIX Version 0 in the last 45 years!) So that the kernel could use the new drive.
And after countless hours of work, the team first uploaded UNIX v0 to PDP-7 owned by Yaryan on Monday, October 28, 2019. Engineers logged in with the username dmr in honor of Dennis McAleystair Ritchie , who created UNIX with Ken Thompson in 1969.
PDP-7 output, including the message: "Greetings from PDP-7, which runs UNIX v0"
At the end of the conversation, Yaryan described what he considers the legacy of his PDP-7, and how he can show people another example of the history of computers: “I want people to know that besides IBM computers there is something else. There have been many interesting stories in my career. ”
Today, visitors can see this PDP-7 and the restoration project at Living Computers: Museum + Labs .