Atlanta's black vote stayed Republican longer than most places

[Indy Texas]

IIRC the Georgia GOP, unlike in most other southern states, often ran candidates in the 1960s and 1970s who were relatively moderate on racial issues.

Bo Callaway did reasonably well with black voters when he ran against Lester Maddox (1968). Hal Suit (1970) was one of the more moderate Southern GOP candidates of that era.

[Indy Texas]

Is there any data on how Mack Mattingly did with black voters in 1980? He won that election on the strength of his performance in Atlanta.

Based on the county results, I would think he probably won blacks in urban areas and lost them in rural areas, but I'm not really sure. a lot would depend on turnout as well.

I doubt that.  Southern urban whites were some of the first white voters in the South to flip to the GOP - look at Ford's performance in Hinds County, MS, for example.  So I'd imagine white voters were pretty right-wing in Atlanta - not to say he didn't do well with African-American voters, but 1980 just seems too late for it to be an outright majority.

It would probably be more accurate to describe them as "suburban" whites.