^No, it's stated quite clearly that Flynn created this new grid from the ground up and brought Clu and Tron over to it. It has no relation to the original movie's grid.
Remember also, Flynn disappeared in 1992 if I recall. So the computer in the basement lab could have tech from at least that year. Much more advanced than 1981.
The thing that gets me is that at the end of the movie we see Sam with a usb key ostensibly making a copy of the "grid". I kept wondering where the hell he was going to plug that in on a computer from - what - 1992 at the latest?