Windows XP 64bit Edition RC1

This weekend I installed Microsoft Windows XP 64bit Edition RC1 on my dual Opteron. So far I am impressed. It's extremely stable and runs all my 32bit applications without a problem. Since Microsoft seems to want to price it the same way as the 32bit version it might easily become the default for new AMD and Intel boxes.

Now, as far as 64bit applications, there is not too much out there. Microsoft ships two versions of IE. Obviously this is because most of the plugins are not 64bit ready yet, including the Flash Player.

After some digging I found some interesting info for developers:

• The Microsoft Windows Sever 2003 Platform SDK has everything required to compile 64bit applications using Visual Studio 2003
• Switching Visual Studio 2003 to a 64bit environment is a little bit of a pain as it is a global environment variable setting.
• Inline assembly is not supported. Instead good old .asm files need to be used.
• In 64bit mode MMX and x87 registers are not saved during a context switch of the kernel. That means that all the MMX code you might have will not run (and not compile that is).
• Floating point math is done using SSE1/SSE2. This could be a problem if you depended on accuracy of the 80bit floating point values of the x87 instruction set. In SSE it's 64bit only.
  
• Custom SSE code needs to be implemented using intrinsics. I still haven't figured out if old MMX code using intrinsics will compile directly to SSE. In theory this should work.
  
• The compiler does output useful information about potentially dangerous pointer usage like casting a pointer to a 32bit integer value or backwards.

I see plenty of work ahead...