I downloaded 64-bit Racket and compared it to my install of 64-bit gambit:

% gsc -v
v4.6.6 20120915144211 i386-apple-darwin10.8.0 "./configure 'CC=/pkgs/gcc-4.7.2/bin/gcc -march=core2 -fschedule-insns -frename-registers' '--enable-single-host' '--enable-multiple-versions'"
% uname -a
Darwin Media-Mac-mini-3.local 10.8.0 Darwin Kernel Version 10.8.0: Tue Jun  7 16:33:36 PDT 2011; root:xnu-1504.15.3~1/RELEASE_I386 i386
% mzscheme 
Welcome to Racket v5.3.

This is a Mac Mini with a 2.4GHz Intel Core 2 Duo and 8GB of ram.

So this is a Gambit with special gcc options that I find generally makes code run faster, at the expense of compile time.  And it uses the latest GNU GCC.

So this is not comparing stock gambit with stock mzscheme; it is not comparing apples to apples.

I applied Matthew Flatt's patch from

https://www.cs.utah.edu/%7Emflatt/benchmarks-20100126/log1/bench.patch

to Gambit's bench script, and then ran "table" from Gambit's bench directory.

This gave me four html files that summarize the cpu and real times to execute the programs; compile times are not reported.

The meanings of the various table titles can be found here:

http://www.iro.umontreal.ca/~gambit/bench.html

I repeat:

So this is not comparing stock gambit with stock mzscheme; it is not comparing apples to apples.

The systems seem comparable running programs in R6RS-* semantics, except for programs using call-cc.

Brad