It starts by looking at the task’s starting address and its priority, then passes that to the NOVAC routine. Scheduling a program falls to the Executive. So in short: twelve words in the Core Set, five words of memory to execute a program, and the seven MPACs deal with the extra information as needed.
They’re called Multipurpose Accumulator or MPAC. The seven remaining words were left for temporary variables or extra storage … whatever they might be.
In each 12-word Core Set, processing information took up five words, one each for the program’s priority, entry point address, copy of the BBANK register, flags, and the last pointed to the Vector Accumulator or VAC area. There were six of these Core Sets in the Command Module and seven in the Lunar Module. This contained all the information to execute a given program. In the case of the Apollo Guidance Computer, it had a 12-word data area called the Core Set. The programs were also scheduled and run based on priority with measures in place to interrupt any program should something vital come up. But between relatively fast processing speed and relatively slow human perception it was simultaneous enough to run the mission smoothly. So how could it run multiple programs - the parts that make up a whole mission event - simultaneously? Well, it didn’t. The Apollo Guidance Computer was a single processor computer, computer. If you’re following along you can see how this creates a potential new problem. These parts or programs were manageable modules that could be run individually while rendering the whole system more reliable. You can start to appreciate how many pieces of information would be going through that computer at any given time.įor the sake of simplicity, each task (a task in this case would be a single mission event like the lunar landing) was broken down into parts.
Alarm for 12 minutes full#
Now think about a full lunar landing mission for a second - getting into Earth orbit, burning the engine to travel towards the Moon, recovering the lunar module, adjusting the course mid-way to the Moon, getting into orbit, landing, leaving the Moon’s surface, and traveling home. It also needed to adjust the abort trajectory constantly, ready to get the crew back into orbit should something force an abort. It needed to maintain the right attitude based on that position, as well as velocity, altitude, and engine performance data. It had to know where the lunar module was and where it was moving, information called state vector. The computer needed to take in a lot of data points simultaneously to facilitate a good landing. This meant the pieces of information could be called up at any time and run nearly simultaneously, which was pretty important. Take the moment of landing on the Moon, for example.
Alarm for 12 minutes software#
The Apollo Guidance Computer in Super Briefīy the time Apollo missions flew to the Moon, the software program that ran the mission could fit - though only just fit - into a set of read-only magnetic cores. So what exactly was the 1202 program alarm that could have killed Apollo 11’s landing? To answer that question, we need to go back and understand a little more about how the Apollo Guidance Computer worked.Īrmstrong training in the lunar module simulator. As we know, Apollo 11 made it to the surface and the alarm has become little more than a story point. Understandably so it was a dramatic moment in an already dramatic event that could have forced an abort and left the commander of Apollo 12, Pete Conrad, as history’s first man on the Moon. The 1202 program alarm is featured is just about every retelling and dramatization of Apollo 11’s lunar landing. “It’s a 1202 … What is that? Give us a reading on the 1202 Program Alarm …” Then came Armstrong’s voice over the radio again, this time marked a slight note of urgency. The room full of flight controllers listened to the exchange while keeping a close eye on the numbers filling their screens, looking for any little anomaly that could force an abort. “That’s affirmative,” replied Capcom Charlie Duke. The mission’s commander was laser focused on getting the spacecraft down onto the Moon’s surface for the first time in history. “Sure do,” agreed Neil Armstrong, adding, “Houston, you’re looking at our Delta-H.” The Earth wasn’t his main concern for the moment.
Alarm for 12 minutes windows#
“Got the Earth straight out our front window.” As the lunar module Eagle yawed into a windows up orientation, Buzz Aldrin looked away from the computer to see the Earth nearly a quarter of a million miles away.
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