Say I have a 64bit program. In order to run it at full 64bit, will it be the case if installed in a 32bit OS with a 64bit CPU? Or It needs BOTH a 64bit OS and CPU? I'm confused...

I can't find any information about this on wikipedia, but I'm pretty sure the 64-bit software is designed solely for use with 64-bit operating systems running on 64-bit processors.

Did a bit of Googling and found this nice explanation...

http://www.velocityreviews.com/forums/t373376-pyt...5-winxp-amd64.html

quote:

---

The O.P. has a 64-bit Athlon processor, but is running a 32-bit OS. The processor emulates its 32-bit predecessor in "legacy mode", so 32-bit software runs.

Given a 64-bit processor, why can't 64-bit applications run under a 32-bit Operating System? Because the O.S. provides the environment in which the application runs. There are several problems: system calls could be probably be thunked by a library, but the virtual memory space is a deal breaker. A 32-bit O.S. deals with 32-bit addresses; it can't support the address space of a 64-bit app.

Running a 32-bit O.S., the processor stays in 32-bit legacy mode. Enabling the processor's 64-bit mode is a privileged operation; the application cannot do it.

---

Mmm...I'm more confused now...there are 64 bit software that runs on 32 bit Os...take the new version of Mathematica as ana example:
http://www.wolfram.com/products/mathematica/newin52/64bit.html

quote:

---

Originally posted by alegator
Mmm...I'm more confused now...there are 64 bit software that runs on 32 bit Os...take the new version of Mathematica as ana example:
http://www.wolfram.com/products/mathematica/newin52/64bit.html

---

In order to run a 64-bit application you need to have both a 64-bit processor and a 64-bit Operating System. If you have a 64-bit CPU, but not a 64-bit OS, then you can't run a 64-bit program. It will just crash.

just one (sort of) exception
VMware can run a 64bit guest OS even if the host OS is 32bit
it's a bit of a different story, but it runs 64bit "under" (actually closer to along with) 32bit.

Windows Vista will be 32bit, so what's so great about it? When do you think that Windows will release a 64bit OS along with all corresponding drivers?

quote:

---

Originally posted by alegator
Windows Vista will be 32bit, so what's so great about it? When do you think that Windows will release a 64bit OS along with all corresponding drivers?

---

Yes, I just read it'll come in both 32 and 64bit versions. Problem is that most drivers today are written for 32bit.

quote:

---

Originally posted by alegator

Yes, I just read it'll come in both 32 and 64bit versions. Problem is that most drivers today are written for 32bit.

---

quote:

---

Originally posted by HSV

quote:

---

Originally posted by alegator

Yes, I just read it'll come in both 32 and 64bit versions. Problem is that most drivers today are written for 32bit.

---

companies will be made to make 64bit drivers for Vista & XP 64bit,

---

Before they are common on (almost) all PCs will take quite some time I think, since *the masses* don't buy a new PC that often. So 32bit will stay with us for quite some time from now.

You can, however, run your 32bit apps on a 64bit OS. So if you want to switch to 64bit, you won't have to buy/download/wait for 64bit versions of all your software and drivers. You can just use all of your 32bit apps and install a 64bit version every now and then as soon as it's stable enough for your needs.

quote:

---

Originally posted by JesusYou can, however, run your 32bit apps on a 64bit OS. So if you want to switch to 64bit, you won't have to buy/download/wait for 64bit versions of all your software and drivers. You can just use all of your 32bit apps and install a 64bit version every now and then as soon as it's stable enough for your needs.

---