Keep in mind aircraft electronics like that was the absolute cutting edge when it was new. As soon as it was practically possible to do stuff like that they did. They are also extremely extensively tested to the point it's a bit insane and all this testing needs to be done for any replacements.

It's to the point some of the basic performance calculations for older aircraft are still done on special purpose slide rules because it's easier than doing it by hand and it would be too expensive to do all the testing for a program that does it on the flight computer.