Advanced Micro Devices Inc (AMD)

[wbmw]

Porting to AMD64 FAQ

http://www.amd.com/us-en/assets/content_type/DownloadableAssets/AMD64_Porting_FAQ.pdf

Some interesting Q&A in here. Looks like there may be more issues with AMD64 than people realize. For example:

Are all 32-bit Windows® or Linux applications compatible with their 64-bit operating systems?

The AMD64 ISA is designed to impose no limitations on application compatibility, but
that doesn’t mean that every application that can run on a 32-bit operating system can
also run on the 64-bit version. For example, Windows64 will not support 16-bit
programs. AMD’s 64-bit processors are designed to run any application supported by
the operating system.
The following rare occurrences could cause compatibility problems with 32-bit
applications:

• Applications that install device drivers may not work correctly if there is no 64-
bit version of the required driver.
• Applications that attempt to share buffers containing pointers may not work;
however, such programs do not follow normal conventions in either Linux or
Windows and are not portable in general.

Are 32-bit device drivers compatible with 64-bit operating systems?

No. Only 64-bit drivers can be used with 64-bit operating systems.

Can you mix 32-bit and 64-bit code in the same process?

No.

Can x87 instructions still be used by 64-bit applications?

64-bit applications cannot use x87 instructions because 64-bit operating systems are
not required to preserve the x87 stack across interrupts and context switches. AMD
has gone to great lengths to ensure that SSE/SSE2 math library performance and
accuracy exceeds that of the x87 instruction set. We anticipate no need to use x87
instructions in 64-bit applications.