impossible → routine
Grandmaster chess
Playing chess above the strongest human players.
Impossible
IBM's Deep Blue beats world champion Garry Kasparov 3.5–2.5 in their six-game rematch in New York.
3.5–2.5 over six games
source12 years, 3 months
Routine
Pocket Fritz 4 scores 9.5/10 at the Mercosur Cup in Buenos Aires running on a handheld Pocket PC, an Elo performance of 2938 that included outplaying a 2522 grandmaster.
9.5/10; Elo performance 2938
sourceThe Week In Chess 131 is dated 12 May 1997 and reports Kasparov's loss in the final game "last night"; game six was played on 11 May. The 2009 end is dated to ChessBase's report of the Mercosur Cup, which is the source for the score, the 2938 performance, the handheld, and the "2522 grandmaster" the program outplayed.
That report does not itself say the program finished first, so the claim is made here rather than in the end above. The HIARCS crosstable for the event records Pocket Fritz 4 in first place on 9½/10, undefeated, ahead of GM Rodriguez Vila (2522), GM Valerga (2507) and GM Slipak (2469), and names the hardware as an HTC Touch HD. The two sources disagree on the field's strength — ChessBase calls it category seven, HIARCS Category 8 — so neither figure is quoted as settled here.
Worth being exact about what the second end shows. Deep Blue beat the strongest human alive; a category 7–8 field is strong grandmaster opposition but not that. What collapsed between the two dates is the hardware, not the standard of play: the same class of result moved from a purpose-built machine to a device that fits in a pocket.