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How Apollo 11′s 1.024MHz guidance computer did a lot with very little

  • Posted on April 6, 2017 at 4:00 pm

 

early 44 years ago computer hardware was in an entirely different place than it is now. The levels of performance don’t even fit on the same scale. The anniversary of the Apollo 11moon landing is upon us, and those brave space pioneers got by without a 3GHz multi-core CPU. The guidance computer used on the Apollo 11 mission ran at only 1.024 MHz.

The moon landing was the height of technological achievement at the time, and some of the rocket technology is still relevant today. That computer, though, has been left in the dust. In fact, it was well and truly obsolete a few years after the landing.

The Intel 8086 came about roughly ten years after the Apollo landing, marking the beginning of x86. Apollo 11’s computer had 4 registers — essentially slots for holding numeric values. The 8086 boosted that to eight 16-bit registers.

The IBM PC XT ran the next version of that chip, the famous 8088. This computer ran at 4.077MHz, which sounds incredibly slow by today’s standards, but is still four times faster than the Apollo 11computer. The XT also packed in eight times the memory used on Apollo 11.

The Apollo 11 guidance computer actually had some impressive software features for a system that didn’t even run a graphical interface. It could multitask up to 8 different operations, but it didn’t work the way we think of multitasking. Today’s operations use preemptive multitasking that allows the OS to distribute computing resources as needed. On Apollo 11, programs were in charge and had to give control back to the OS periodically. A kind of virtual machine was used to allow developers to mix hardware-level instructions with virtual machine commands within the same assembler code.

Inputting commands required translating the English words into “verb noun pairs,” which could be input as numbers. There was a handy sign in the cabin as a reminder. To top it all off, none of the computer’s systems were software upgradeable. All the code was stored in read-only memory. Several years after Apollo 11, Apollo 14 was forced to manually input the code to patch a system malfunction — it took 90 minutes just to type it in.

Maybe your computer is a little sluggish, and your smartphone is a couple years old, but you have it better than those astronauts