I just found out the hard way that in 32 bit programs under Win64, the value of CS changed. In Win32, the value of CS is 0x001B. In 32 bit programs under Win64, it’s 0x0023. This will probably break some programs, especially debuggers.
Why did Microsoft do this? It’s not like the value of CS is undocumented: it’s in the DDK as KGDT_R3_CODE, and I’ve seen it several times in other places on MSDN. I can’t see any reason that they changed it. The 64 bit CS didn’t replace it – the 64 bit CS is 0x0033.
Normally I wouldn’t post 2 things in 2 days but this just really annoys me.