An x64 CPU can run either x86 or x64 operating systems. Indeed, x64 may be considered more of an "extension" to x86 than something new and totally different.
Again, there is no mechanism to prevent an x64 processor from working with a 32bit or even 16bit operating system, just as 32bit processors can run 16bit operating systems. When it comes to code execution under those operating systems, again, there is no CPU dependency. 16bit applications/installers will continue to work under the x86 version of windows, and 32bit applications will continue to work under the x64 version. However, Windows x64 -does- require that all driver code be 64bit. Does that help? Greg > -----Original Message----- > From: [EMAIL PROTECTED] [mailto:hardware- > [EMAIL PROTECTED] On Behalf Of Jeff Lane > Sent: Tuesday, December 19, 2006 8:25 PM > To: The Hardware List > Subject: Re: [H] CPU-64 or 32? > > Just a little confused. You are saying that he has to run the 64bit OS > version on the 64bit CPU and cannot run the X86 OS version on that > processor, otherwise all will run as X86 if installed on the 64bit? > > ----- Original Message ----- > From: "Wayne Johnson" <[EMAIL PROTECTED]> > To: "The Hardware List" <[email protected]> > Sent: Tuesday, December 19, 2006 5:08 PM > Subject: Re: [H] CPU-64 or 32? > > > > At 06:55 PM 12/19/2006, Jeff Lane typed: > >>If I build a 64bit processor system can I run only X86 OS and S/W? > > > > No. > > > >> If so, will all the X86 drivers operate as in a normal X86 system? > > > > Yes. > > > >> In other words, is there automatic backward compatibility? > > > > Yes. > > > >>The reasoning here is that if he does decide, or need, to change to the > >>64bit in the future he will just have to change OS version and, maybe, > >>some S/W, rather than build a whole new PC. > >
