"STORED PROGRAM CONCEPT" Sometimes referred to as, Stored Program Control.
In the beginning “doing sums” consisted of counting sticks, pebbles,
moose droppings, and fingers & toes.
After a few thousand years of this, somebody shows up who got real tired,
real fast of this crap, and started looking for an “easier way"—not a better
way, but a way that would give him more 'ponder time.' First thing
he did was to start pondering “what's better than rocks, fingers and toes,
and moose droppings.”
At the same time there were others equally fed up, people looking for
the same thing. Some folks were successful, some were not. The upshot was
varied gadgets that, more or less were the beginnings of the first calculator.
Needless to say, the first calculators were mechanical calculators--machines.
The next improvement was to speed up the process by using electricity
with electric relays (using base-2 notation). Of course, like the
mechanical calculators, they were “hardwired” to only do a fixed set of
To make them more versatile, plug boards were introduced to alter
the machine's operation for different functions. Though an improvement,
it was still very limited functionally and slow.
The mechanical “engine” was replaced by vacuum tubes which made
the calculating engine much faster, smaller and more reliable.
By substituting the Jacquard loom's (1804) programmability for
the plug board, you have one of the first incarnation of “stored program
The great need for adequate storage was a constant, and was met
with varied solutions, albeit seemingly tortured at times— punch cards,
paper tape, etc., moose droppings...
The advent of magnetic storage: magnetic drums, magnetic core,
magnetic tape, etc., along with ever more reliable vacuum tubes filled
the gap before the silicon era.
As with all successful innovations, it was a confluence of maturing
technologies, as well as geopolitical pressures, that came together enabling
the creation of SAGE.
Computer's Units: Arithmetic-Logic Unit
Bus (data path)
Sequence of Operation
Fetch the next instruction from memory at the address in the program
Add 1 to the program counter.
Decode the instruction which commands the rest of the computer to perform
some operation. The instruction may change the address in the program counter,
permitting repetitive operations. The instruction may also change the program
counter only if some arithmetic condition is true, giving the effect of
a decision, which can be calculated to any degree of complexity by the
preceding arithmetic and logic.
The Modern Computer's evolution is as varied and complex
as any, and there is no way in Hell I and my web page can do it justice;
however, there was a seminal event in that evolution that had a profound
effect on today's modern computer, and that was "Semi-Automatic Ground
Environment," or SAGE for short.
SAGE, an air defense
shield for North America was an integration of all the relevant technologies
and inventions of the day, plus the countless technologies that SAGE
I will attempt an introduction to the marvel that was
the SAGE Computer, a.k.a., "son-of-whirlwind," a.k.a., AN/FSQ-7/8. Given
the constraints of 1950's technology, i. e., it weighted 250 Tons, took
up 113,000 sq. ft., required 3 Megawatts to power the 200,000 vacuum tubes
that was cooled by 25 million BTU of AC, at a total cost of $65 to $100
billion (in today's dollars), and was staffed by over a thousand.
The real marvel of SAGE was that they were able to design,
develop, and field ~23 functioning sites given the technology of the day.
In the decades since SAGE,
very few could have imagined the advances that has given us today's incredible
Air Defense, Cold War era The World's Largest Computer The U.S.
Air Force's IBM
Computer circa 1958
Environment SAGE stands for Semi-Automatic Ground Environment. Because, back then,
Computers were so limited
the system's only hope of working depended on the "Man in the Loop,"
hence the term Semi-Automatic.
SAGE Blockhouse/Computer: 113,000 sq ft., 250 tons, houses More than
200,000 vacuum tubes @ 3,000,000 Watts
Typical SAGE Direction Center
At nineteen years
of age (circa 1957), I worked in a SAGE facility (DC-04) located at Fort
Lee, Virginia (near Petersburg), as an installer for Western Electric
Company (WECo). Our job was to install all of the Communications equipment
that occupied most of the first floor. The remaining three floors housed
the computers, display consoles, administrative offices, and USAF crew
Satellite shot of the old Fort
Lee SAGE building today
A lot of the information on SAGE is anecdotal and conflicting, as well
as, from my memory of 55 years ago. Of course, as SAGE matured the numbers
did change; it was operational from ~1958 - 1983.
my job as the youngest Installer in a group of old salts, I was often the
butt of jokes and the derision sometimes given to the young by the "veterans."
Also, as I was to find out later, a lot of the mistakes made in the installation
were blamed on me.
I discovered this one day after the completion of an unusually large job
at the U.S. Air Force's SAGE air defense filter center, at Fort Lee, Virginia.
The project manager--Captain Cook, a rather stern man whom we all were
a little afraid of, gathered all the employees for a mass meeting. Out
of the blue, he called me up to the front. Standing behind me with one
hand on my shoulder, he said that the installation was ahead of schedule
and was a success, and that he wanted to thank Williamson especially, for
"single-handedly installing the office." He said that he knew I had single-handedly
done the job because every mistake found in the entire installation had
been blamed on him, therefore "he must have been all over the place."
I was stunned! But of course I knew that was just his way of putting some
Wise Asses in their place, never the less, my stock had been elevated for
a while at least.
From that day on, I was seldom blamed for other people's mistakes...
building, which was aboveground, was considered "Hardened" (to the effects
of limited bomb blast). When we were installing some equipment in the first
floor telco area, I had to drill several holes in the concrete floor, 5/8"
in diameter 1 1/2" deep. I got a real insight into how hardened the building
really was; after 45 minutes and two star drills later, I was only half
way through. If I was doing it by hand I'd still be there.
After WWII and the onset of the "Cold War," there was a pressing need
for a perimeter air defense around the United States/North America. Due
to the numbers and speed of the threat, some sort of automation was seen
as the great equalizer. Automating the plotting, targeting, and the interception
of high speed enemy bombers was the strategy of the day.
The USAF enlisted MIT's help in it's design, along with several companies
for it's development, manufacture and deployment. The result was the construction
of 23* concrete-hardened "Direction Centers" across North America linked
through each's AN/FSQ-7 air-defense computer system designed to detect
Soviet bombers and guide interceptor aircraft and ground to air missiles.
Thus was born SAGE, or Semi-Automatic Ground Environment. Because, back
then, computers were so limited the system's only hope of fulfilling it's
mission depended on the "Man in the Loop," hence the term “Semi-Automatic.”
The plan was to create a North American radar perimeter of air defense
sectors, each controlled from a SAGE station with its own AN/FSQ-7/8 computer.
In 1957, the first SAGE station became operational. By 1961, the system's
23* sectors were complete. From the Canadian border to the Arctic Ocean,
radar networks tracked aircraft, sending radar data
from the networks to the SAGE stations over standard leased telephone lines.
The SAGE stations guide interceptors and missiles to all targets.
U.S. Air Force SAGE Project Office, Air Material Command, NORAD,
Air Research & Development, Air Training Command.
MIT Lincoln Labs, SAGE Design, R & D, and integration etc.
MITRE, for system integration, R&D.
IBM, design, development, and manufacture of hardware.
Burroughs, AN/FST-2 radar data processor/network, ALRI system.
Western Electric Company (WECo) Winston Salem, for communications
Bell Telephone Laboratories (BTL), SAGE effectiveness evaluation.
Western Electric Company (WECo) New York, work with USAF to
coordinate and manage the entire effort. Also, design and construction
of Direction and Combat Center buildings, and testing of the system.
System Development Corporation (SDC), (part of the RAND Corporation)
developed computer programs, training AF crews to run & maintain, etc.
In the 1950's MITRE's founders played a key role in the development
of the Semi-Automatic Ground Environment (SAGE) system, the first major
real-time, computer-based command and control system. Designed as a new
air defense system to protect the United States from long-range bombers
and other weapons, the SAGE system sent information from geographically
dispersed radars over telephone lines and gathered it at a central location
for processing by a newly designed, large-scale digital computer. As the
system evolved, SAGE broke new ground in radar, communications, computer,
information display, and computer programming technologies.
In 1958, the MITRE Corporation was formed out of the Computer System
Division of Lincoln Laboratories. Much of MITRE’s initial work focused
on the software development of SAGE’s digital computer system, radar surveillance,
communications, and weapons integration. More importantly however, MITRE
had the role of integrating many elements of the SAGE system
Some of the more impressive numbers:
It weighed 250 Tons.
Took up 113,000 sq. ft. of floor space.
Used a maxamum of ~200,000 vacuum tubes--60,000 tubes for each of two CPUs
(later, 13,000 transistors were added),
Maximum power requirements was 3,000,000 Watts.
It required two huge diesel powered air conditioners (capable of dissipating
heat from 3 Megawatts).
Note the modern-day laptop on the kick-guard below. By any measure,
the laptop is 80,000 to 1,000,000 times more powerful than the computing
power in the entire building!
(SAGE Clock =166kHz:: i7 Intel 3.3GHz x
4 (core) = 80,000 Ratio)
Rack after Rack of Vacuum Tubes that make up a small part
of SAGE's Computer
The 'Blue Room' was off limits to all except those who had the highest
clearance. We had heard of a Major that had strayed over a security yellow
line, he was placed under arrest and sweated for 9 hours striped
to his boxers. Looking back I think the story was fake to scare the troops
straight, back over the yellow line.
Anyway, one day I went to the "Blue Room" to buzz some circuits, I was
escorted by a Air Force guard who was supposed to stay with me, but he
left. After a few minutes the room filled up, the lights went down and
some special top secret tests started up. The tests lasted for over an
hour. In the meantime it dawned on me that I had NO business in that room
and I started thinking about the Major. I couldn't remember if I had put
on clean underwear that morning or not.
computer not powered and the air conditioning running full blast, you needed
to wear a jacket; with only the "filaments" turned on a T-shirt was almost
too much; and when the plates were also powered, safety barriers went up,
the heat was too intense for anyone to linger between the closely spaced
bays of hot vacuum tubes. It was estimated that if the air conditioning
were to fail, the computer would self-destruct in less than 60 seconds.
Magnetic Drum Memory
SAGE AN/FSQ-7/8 Computer Maintenance Control Room .
All Communications goes through
the First Floor, Western Electric's Installation
SAGE relied so heavily on North America's switched telephone networks,
in the early fifties the Eisenhower administration prevailed on AT&T
and the Bell Telephone System to automate and harden their telephone exchanges
and Central Offices (CO) against the effects of a nuclear attack. This
also included Bell Canada. The idea was that after a nuclear attack no
one could inhabit the surviving telephone facilities, that the telephone
system should operate, unmanned, for at least three days.
This was helped along by the development of Direct Distance Dialing (DDD),
DTMF tone dialing, as well as, crossbar switching (No. 5 crossbar, 5XB).
The new buildings were hardened and made windowless, and the preexisting
ones were reenforced. Part of that hardening was how the equipment racks
were secured to both the concrete floor and the concrete ceiling.
There was a CO were a boiler had exploded, taking out the walls, and the
equipment--still standing, continued working, no problems.
To ensure the office would stay operating for the required three plus days,
the backup power supply was improved with the addition of diesel generators
and improved lead acid batteries.
With all of these improvements to telephone service brought on by America's
defense needs, few citizens realized the real reason.
The Blue Room's 20" vector displays were hard for the operators to read
due to the very slow refresh rate, and they were subject to ambient light
glare. To help overcome this, the scopes’ CRTs used long persistence P-7
type phosphor and the viewing room was equipped with special non-glare
indirect lighting at low intensity.
Since the ceilings were twelve feet, special dropped ceilings with recessed
indirect lighting were used. The real secret to its success was a thick
honeycomb light baffle that was suspended above the scopes, they eliminated
any direct light capable of glare.
One other thing that helped, a lot of the operators were former radar
scope jockeys and they were experts at reading dim painfully slow sweep
Honeycomb light baffle was ~6" thick with 1/4" holes
Operator having to interpret a dim scope display,
that had a refresh interval from 2 sec. to 15 sec. The long persistence
of the (P-7) phosphor helped.
centers continued to operate by the FAA/ATC until 1983, more than 20 years
after its technology was obsolete and its mission rendered militarily insignificant
by the ICBM. As a final bit of irony, in the last years of its use, replacement
vacuum tubes had to be purchased from Soviet-bloc countries where they
were still being widely manufactured.
The real effectiveness
of the SAGE system has been debated over the years. Critics saying the
system would have failed to protect the US in an all out saturation bombing
raid, and that SAGE was a giant waste of money.
As to its effectiveness.
the deterrent impact of SAGE on Soviet strategic thinking made any preemptive
strike less likely.
As to it being a waste
of money, aside from the enormous technological strides that helped to
usher in the "information age," the fact we never had to use it in anger,
ever, is proof of its worth.
To Separate Friend from Foe: By means of a grease pencil drawing on the
console's display, Radar target data is correlated with posted near-realtime
ATC flight plans, all of which is imaged by a photo-electric tube mounted