I choosed the dhry-example, compiled it by dmd32 0.82 under WinXPPro64Sp1 on AMD Athlon 64 3200+ and run the resulting executable on the same machine under Win32 and Win64 respectively.

I took 20 runs under each BS (results in zipped .txt in the attachment). All results in millions of Dhrystones/second:

          Average  Stddev
Win32:    1.92     0.00
Win64:    1.91     0.01

As the B-splined normalized data shows, the distribution of values seems quite similar. ( zipped jpg in the attachment).

So long!