Well, I never said he was good good, but it at least surprised him that he wasn't able to make any headway against the program. I'll leave it to someone who actually understands chess and happened to play the thing themselves to determine how objectively difficult it really was.
My brother tried fiddling around with an Atari 2600 version of chess on GameTap a while back. He's no grandmaster, but he's at least decent in the game, so he figured he'd have a good shot of winning. He must have had the game mode set on the hardest difficulty level, because that damn ancient AI obliterated him every time he played. The most amusing part for the non-chess-playing me was watching the game screen flash psychedelic rainbow colors every time the computer "thought" about its next move. Who knew those cartridges were so advanced?
I don't want to be insulting, but the hardest setting in a chess playing game from a console from the late 1970's shouldn't be difficult. Most likely your brother wasn't as good as he thought, or he was having a really bad day.
That's the thing, you don't have to be a good good player to beat even a fairly good chess game from that time. For example, Kaissa was an average engine at that time, it had an ELO rating below 1700. In 1980, Belle had a performance around 2250, master level, but just with one problem, besides being by far the strongest computer in the world at that time, it used dedicated hardware. From what I gather, Chessmaster 2100, one of the strongest engines available for the Amiga, had an ELO rating below 1800 (this take from the fact that Chessmaster 3000 had an ELO rating of 1800).
The average (club) player have an ELO rating around 1800. So to stand equal to that chess engine you'd have to... average. To be slaughtered...
Damn, I never knew it was that hard to get ELO ratings of engines from that long ago.
I have no idea how I confused the Atari 2600 for the Amiga, but I assume the point still stands.