Yes! Unfortunately, the default for the compiler we used[1] to align struct members on DWORD (32-bit) boundaries, for some technical reason I am sure was total

Yes! Unfortunately, the default for the compiler we used[1] to align struct members on DWORD (32-bit) boundaries, for some technical reason I am sure was totally reasonable. And these guys all built their code with a special make-variable that appended the "don't-pad-structs-I-really-know-what-I-am-doing" flag to the compiler's command line. I did read somewhere, that x86 (at least Pentium III and later) like to make memory reads from addresses that are a multiple of four. But the profiling data I was able to gather showed that that part of the application had a negligible impact on overall performance. Since the vague job description I had gotten said my job was to "make things faster", I decided not to look into this any further. [1] OpenWatcom (http://www.openwatcom.org/ http://www.openwatcom.org/)