what is difference between 32 bit vs 64 bit OSs and processors (Intel architecture and WIndows)

The only difference I know is that size of the registers for 64-bit and 32-bit processors are 64 and 32 bits, respectively. Also the addresses are 64 bits in 64 bit processors. Are there any o开发者_开发知识库ther differences between these two?

x86_64 has more registers than x86, so more work can be done on the CPU rather than constantly fetching bits from RAM. Also, x86_64 guarantees that the CPU supports at least SSE2, so the compiler knows it can optimize for that.

Those are the key differences, but those differences have many effects - for instance, since addresses are larger, the amount of memory you can effectively access is greater - 32-bit OSes are traditionally limited to around 4GB of memory.

In 32-bit machine the maximum size of RAM will be 4GB 2^32=4294967296 bits which equals to 4GB

but in case of 64-bit machine this will be- 2^64=18446744073709551616 bits which equals to 17179869184 GB

Physical Address Extension (PAE) is a feature to allow x86 processors to access a physical address space larger than 4 GB. This can go up to 64 GB. To use PAE, the OS must support this feature. All major OSes allow the use of PAE, including Windows.

Hence, memory access can't really be held as grounds for distinction between 32-bit & 64-bit OSes.

On the other hand, almost all the processors coming now into the market are 64-bit capable, so it really depends on your OS, how much memory access it allows.

The main difference between 32-bit processors and 64-bit processors is the speed they operate. 64-bit processors can come in dual core, quad core, and six core versions for home computing (with eight core versions coming soon).

Multiple cores allow for increase processing power and faster computer operation. Software programs that require many calculations to function operate faster on the multi-core 64-bit processors, for the most part.

It is important to note that 64-bit computers can still use 32-bit based software programs, even when the Windows operating system is a 64-bit version.

Another big difference between 32-bit processors and 64-bit processors is the maximum amount of memory (RAM) that is supported. 32-bit computers support a maximum of 3-4GB of memory, whereas a 64-bit computer can support memory amounts over 4 GB. This is important for software programs that are used for graphical design, engineering design or video editing, where many calculations are performed to render images, drawings, and video footage. One thing to note is that 3D graphic programs and games do not benefit much, if at all, from switching to a 64-bit computer, unless the program is a 64-bit program.

A 32-bit processor is adequate for any program written for a 32-bit processor. In the case of computer games, you'll get a lot more performance by upgrading the video card instead of getting a 64-bit processor.

In the end, 64-bit processors are becoming more and more commonplace in home computers. Most manufacturers build computers with 64-bit processors due to cheaper prices and because more users are now using 64-bit operating systems and programs. Computer parts retailers are offering fewer and fewer 32-bit processors and soon may not offer any at all.

Extract from : Here.