Other information I found in some of my books and online show that the AFICS manufacturer Honeywell started work on the DAFICS in 1980 and it flew operationally in 1983 replacing the less reliable and slower analog system.
Read: "SR-71 revealed: the inside story" By Rich Graham
The Thud had a navigation computer too, but I believe it was analog from everything I've read.
Keep 'em flyin'
[Airplanes are] near perfect, all they lack is the ability to forgive.
— Richard Collins