What is the Elo of the Mac Book chess engine at top strength?

Solution 1:

The Mac chess app is based on the Sjeng engine.

A page on the Sjeng website says:

Sjeng is probably a bit weaker in bughouse than it is in crazyhouse. Most Sjeng's on the FICS have a rating of about 2000 points in bughouse, with a top of over 2200 points.

For standard chess, Sjeng's rating is probably about 2450 ELO [sic]. In suicide and losers chess Sjeng beats all but the very best humans, and will beat non-specialized programs easily.

So, according to the makers of the engine Apple uses, the Elo is around 2450 in standard mode.

Solution 2:

From my limited testing and reading it seems to be in the 1600 - 1900 range, but of course I might be completely wrong because I don't play chess that often.

As far as I know, there's no information on what the real ELO is.