No, fast C in the 80's and early 90's meant writing code that was actually like this:

    naked void my_C_func()
    {
      asm {
       ...
      }
    }

Which basically meant using C as a poor man's macro assembler and nothing to do with what ANSI C is.

There were also other tricks related to unions and bit fiddling.

In those days, on 8 and 16 bit home computers, C was seen like managed languages are nowadays.