National Museum of Science and Technology

Last week, I visited the National Museum of Science and Technology in Ottawa. I had not been there since I was in public school so many years ago. There is an exhibit called the crazy kitchen, which is a room built in strange angles vertically and horizontally and with interesting perspectives. It challenges your sense of perspective and balance. I remember that room from 50 years ago. Go see it if you never have!

The Museum is the final resting place for the GE-115 computer from my high school. In 1980, the computer was donated. It was dismantled, crated and shipped and has been sitting in the warehouse ever since. I should mention that the warehouse is a massive storage facility which houses all kinds of technologies, including trains and automobiles!

I met with Cédric, who is part of the team of curators in communication technology. He kindly arranged to show me some of the artifacts that were both meaningful and easily accessible. In our earlier discussions, we agreed that it did not make sense to pull out the crated devices simply to look at them and reminisce. They had some manuals which were stored separately, and I had the privilege of looking at them.

I did my best to manage my expectations about this visit. I imagined it would be awesome and very emotional to see the things which I had know and lived with so long ago. However, I thought there might be a possibility of disappointment as well. It turns out there was a little of both!

When I arrived, Cédric took me to a work area that they use to view artifacts. He had laid out several documents on a table for me to look at. There were two GE-115 manuals, a copy of a paper and some punched paper tape. I was a bit disappointed that there weren't more manuals to look at, but I was excited to see the contents of what was there.

I wore plastic gloves when handling the paper, in order to help preserve the paper. This helped me to understand the importance of preservation, a goal which became more and more important to me as the afternoon unfolded. The first manual I looked at was the GE-115 System Manual. I had a digitized copy from the Computer History Museum from 1966. This manual was from 1969, and was slightly different. I worked through the manual, and took pictures of the pages were I noticed a difference between the two. 

The System Manual was originally written for the Gamma 115. You can see that the term "GE-115" is typed in a slightly different font, and would have been the product of a typewriter over some kind of correction tape. This is similiar to the other manuals at the Computer History Museum, and I found a couple of spots where they missed making the change, and the original Gamma 115 was still visible.

The 1969 manual had nearly identical pages, but had been updated to include the GE offerings, such as the disk operating system. It was indeed a special moment to re-read a manual which I knew I had read before and was part of my history. It also included a long list of subroutines which were available in the APS programming language to extend the functionality of the CPU. For example, the CPU does not do native signed binary arithmetic, but there are subroutines for accomplishing this. Similarly for packed decimal operations, multiplication and division, i/o routines for paper tape, disk and card devices, support routines for Fortran and Cobol, etc. There were a couple of routines which were quite interesting .. for example a routine which handled upper and lower case I/O. This is interesting because the CPU only defines the upper case alphabet. At some point, this was extended by software to include lower case.

The second manual was DSS130 Recoverable Disk Storage Subsystem, which describes how the data was stored on disk, including rotation speeds, access time and parity bit checking. It is the key to pulling data from a removable disk, something which might be possible to try if we are able to locate an actual disk.I took pictures of several pages, and will find a way to post those somewhere. It would be very interesting to emulate the disk subsystem, and there is enough information here to make that possible. What is missing from the picture still is the formatting of information on the disk itself. I know there was a disk header which had the volume label and an indication if it was a "system" disk or not. A system disk had the BIOS and command handler in core image format so that it could be immediately loaded into low memory and executed. Data disks did not have this image, which freed up space for information. It is important to remember that these disk had a maximum capacity of about 45 million characters, so space was a precious commodity. Of course, there is a file allocation table as well, which showed the locations of the files stored on the disk. If I recall correctly, cylinder 0 of 200 was reserved for the boot image and the file access table.

When I looked at the paper tape, I assumed that it was not relevant, since the machine that I worked with from 68 until about 75 did not have a paper tape reader. I may have jumped the gun on this one, as it is entirely possible that a paper tape reader was added after that time. I did not see a paper tape reader in the manifest of artifacts, so this supports the idea that the paper tape may belong to some other computer at the museum. 

Finally, there was a diagram which had been created by the people who packed up the computer for shipment. It showed the floor layout of the computer and identified the pieces by name and by catalogue number. I was confused at first, since some of the pieced appeared to be in the wrong place. On the drive home, it occurred to me that they must have pulled the pieces apart to separate the wiring, and that the museum then catalogued those pieces from where they were sitting on the floor at the time of packing, rather than where they fit into the operating configuration for the machine.

Observing all of these things made the trip well worth the effort. However, the next conversation I had with Cédric fundamentally changed the way that I look at this project, and my sense of what needs to be done next. More on that shortly!!

Jim