abstract graphic imageCARE logo

Home | About CARE | Newsletter | Reunion | Member Directory | History Project | Resources | Support CARE

Table of Contents



Support CARE


CARE Member Contributions to The Next Thirty Years

The Day the Computer Stopped – Almost Permanently!
Submitted by Bill Threlfall
District and Chabot College

One of my most memorable experiences occurred in 1992 as I began new duties as Chief MIS Officer for the Chabot-Las Positas Community College District. Though I had been an active user of computers for years at Chabot and had led the selection process for the District's new hardware and software, in my new job I assumed full responsibility for all administrative computing in the District. Two days after I started, I thought I might be fired. The story has a bit of detail, but I'll try to keep it non-technical:

I started duty on a Thursday, getting my feet on the ground. When I entered the office on the following Monday morning, the staff who were already present had long faces and downcast eyes. They explained that the air conditioning system for our ancient main computer, the "DEC-10", had failed over the weekend, resulting in 95 degree temperatures in the computer center. The DEC-10's disc drives could not tolerate such temperatures, and several were severely damaged. Significantly, one of these was the "boot" drive, which is used to start the system and load its operating system software into memory.

During Monday, all the drives were repaired by Digital Equipment Corporation (DEC) technicians. Now all we needed to do was (1) start the computer and (2) restore the contents of the repaired drives from backup tapes…

For the failed disc drive that starts the computer, we had spare disk packs that could be quickly mounted in the drive by the computer operator, providing prompt restoration of service. Unfortunately, neither spare pack proved readable. We were only able to start the computer using the original DEC factory system pack, but using it we were "up" and running!  However, this was the equivalent of returning your home computer to the condition it was in when you first took it out of the box and started it up; we had no programs or data available – just a bare factory release operating system.

Now it was time to restore the contents of the rest of the repaired disc drives from tape backups so that all our programming and data would be available. These data included registration information, personnel information, accounts receivable and payable information, etc.

Where were all these programs and backup data? On the backup tapes. Here comes the problem: By 1992, the DEC-10 was obsolete, having been out of production since 1983. To update it, our staff had installed newer "high-density" tape drives that outperformed the original ones, and they had modified the computer's operating system to allow it to use these high-density drives. Unfortunately, when we started the computer from the DEC system disc which lacked those modifications, it could not read the backup tapes.

I asked, "Where is the modified version of the operating system which can read the tapes?" The answer was, "On the tapes!"  This was extremely bad news, because it meant the software required to read the tapes was stored on the tapes we couldn't read – "catch-22".

We were down nearly two weeks. During most of this time, it appeared that we were facing possible disaster – that all registration, personnel, and finance data would be lost permanently, along with all the programs written by our staff over the past decades. DEC sent an engineer from Colorado who was unable to resolve our problem. We had nearly exhausted all options when Eric Stricklen, our systems administrator for the DEC-10, found an old 8" floppy disc that contained the high-density tape drive modifications we needed. Once those were restored to the system drive, we could read the backup tapes and the full system was back up soon thereafter.

Whew! A rough start to a new job…


I took two key lessons from this experience:

First, a commitment to keep the operating system of our new computer (that was being installed to replace the DEC-10) in an up-to-date and unmodified condition, so that in an extreme emergency, we could restore our tapes to similar computer hardware at another site.

Second, an understanding that our most important asset was the magnetic image of data and software on our backup tapes, and that we must take every precaution to guard the integrity of that backup image: off-site backup storage, fireproof vault for tape storage; test restorations, etc. Our practices followed those lessons during my years at CLPCCD MIS.

About the DEC-10

Digital Equipment Corporation was a key player in the mainframe and mini-computer business of the 1970s and 1980s. The DEC System-10 was the company's flagship product until it was discontinued in 1983, after being superseded by the VAX minicomputer systems. DEC-10s were leaders in establishing "time-sharing" by multiple concurrent users and were popular in academic settings.

Our DEC System-10 was originally purchased in the 1970s and went through two subsequent upgrades. In its final configuration (KL-1091), it was about the size of seven refrigerators and seven washing machines and required a dedicated room with fire suppression and air conditioning. We had spent about $1.8 million on its purchase and upgrades (in 1992 dollars). When its service ended in 1994, it was worth nothing; we were lucky to find someone who would disconnect it and haul it away without charge. Half of it went straight to the dumps.

By 1992, factory maintenance for our district's DEC-10 cost $93,000 per year, with an additional $16,000 per year for air conditioning and electricity to run the machine. It broke a lot, mainly because there were frequent power failures on the Chabot campus and these almost invariably caused some damage, despite our use of a large battery backup power system.

Our DEC-10 supported 128 concurrent users via serial ports, but it had no network capability. Today's typical $900 laptop computer has both wired and wireless network connections and about 100 times as much memory and 200 times as much disc storage as our DEC-10.

Wikipedia provides a fine history and technical description of the DEC System-10, also known as the PDP-10, at http://en.wikipedia.org/wiki/PDP-10 

Return to Table of Contents


©2007 C.A.R.E.

Home | Contacts | Privacy Policy