Please Explain 64-bit vs 32-bit

[Jafo]

Please explain the differences in the use memory of a 32-bit OS and 64-bit.

[Athildja-x64]

In a 32 bit OS the memory addressing is in 32bit blocks (32 pieces of data or 32 1s or 0s).
In a 64 bit OS the memory addressing is in 64bit blocks this allows for roughly twice the amount of data per memory address making a 64 bit OS more memory efficient.
That is the most basic difference

[Jafo]

So, does a 32-bit OS limit the amount of memory available for use or just the efficiency in the use of the memory?

[screwballl]

32-bit is limited to maximum 4GB by the system but the OS itself may have other limitations. 64bit is scalable up to 64TB IIRC.
But when you compare native 32 bit app and a 64-bit app, you will see that the 64-bit tends to run a bit faster and smoother overall.

[gvblake22]

Here is an in-depth article outlining the differences between a 32-bit and 64-bit operating system...

[Athildja-x64]

that article is another simplification of it.
TBH there is a lot that is different, As mentioned above 64 bit applications tend to run faster and soother than their 32 bit counter parts.
Thanks to AMD we have a hybrid that helps to smooth the bridge from 32 bit to 64.
this is the x86-64 instructions.
AMD calls is AMD64 Intel calls it EM64T. it is the same thing though.
You can run most 32 bit applications on an x86-64 system without the need for emulation.
Now while you will see some improvements running a 32 bit application on a 64 bitn system and see improvements with an application that has added the extra memory registers, where you see the biggest improvements is where the applications is compiled to run natively in 64bit mode.
As an example take a look at these POVRay scores

QX6850
Vista x86 - 1666.75 PPS
Vista x64 - 2080.47 PPS

QX9650
Vista x86 - 1883.65 PPS
Vista x64 - 2404.35 PPS

Now as you can see the native 64 bit version of POVRay does much better in the multi CPU render test.