The difference between 32-bit vs 64-bit ProcessorFundamentals

By Maduranga Jayasinghe | 2016, November 24  Views : 182

මෙම පිටුව යාවත්කාලීන කරමින් පවතී...

Do you have a new computer, sophisticated mobile phone or table? Have you see that big marketing sticker on it that says "64bit"? Did you think what is this "64bit" and it's really important to your device?

Even though 32bit and 64bit most popular keywords during past decade, do you know that there are 8bit and 16bit processors in the market? Besides, 128bit processors too. There are a lot of embedded systems are still worked on 8bit or 16bit processors. Usually, when we hear something about the new processor, we immediately assume that the latest one is the newer and faster one. Is it true? No. It's not true all the time.

Here I'm going to explain following things you to get to know about 32bit and 64bit processors.

  • what is 32bit processor
  • why needed 64bit processor
  • Does your device really need a 64bit processor?

1.) what is 32bit processor

32bit means the number of bits in a processor refers to the size of the data types that it handles, and the size of its registry. In other words, 32bit processor can handle the maximum size of 4GiB of computational values. 32bit causes limiting the RAM size to 4GB.

2.) why needed 64bit processor

No other reason than its memory limitation. You know now that 32bit processors' have a serious hardware problem and it comes from the architecture. That fault cannot be fixed using software patch. But using PAE feature which has provided by later Pentium Pro processors can be accessed memory up to 64GB. I'll explain this later. Well, basically, this is the reason processor makers move to the 64bit architecture and has introduced 64bit processors to the market. A 64bit processor is capable of storing over four billion times as much as the memory than the 32bit processor. In order to get the best performance, operating system also needs to be redesigned to take advantage of the greater access of memory. For an example, If you have a 64bit PC with more than 4GB RAM, try to install a 32bit version of windows operating system on it and check the maximum usable memory it displays. With an increase in the availability of 64-bit processors and larger capacities of RAM, OS developers (Microsoft, Apple, Ubuntu, etc.) had to develop and release the 64bit version of their operating system to give full advantage of the new technology.

Look at the picture below. Here Windows 7 32bit OS has installed on 4GB RAM PC. It says "Install memory(RAM): 4.00GB (3.39 GB unusable). Computer Properties displayed installed memory as 4GB but at the same time stated that only 3.39 GB is usable. So, where did the remaining memory go? NO worries, This is not the 32bit architecture problem. You know that some resources in your computer has reserved memory and is not allowed to access to the operating system, especially graphics adapter.

But, What if you have more than 4GB of memory? Even on a system with 8GB of memory, 32bit windows displays less than 4GB of memory. This is a known limitation of the windows, especially Vista and 7 versions.

Using 32bit registers 32bit processors can be only able to address up to 4GB of memory(232 = 4G). But this is not actually the truth. The reason is the feature call Physical Address Extension or Page Address Extension (PAE) . PAE was first introduced in the Pentium Pro. It defines a page table hierarchy of three levels, with table entries of 64 bits each instead of 32, allowing these CPUs to access a physical address space larger than 4 gigabytes (232 bytes). - Wikipedia. PAE increase its possibility to address more than 4GB of memory using same 32bit registers because the registers aren't used to store the physical addresses. Instead of that, the registers store linear addresses which are mapped to physical addresses using the page table. This feature has available since the days of Pentium Pro has released. These processors provide additional address lines and that can be addressed up to 64GB using PAE future. If you really interesting in windows memory addressing or if you want to learn more follow this link here

3.) Does your device really need a 64bit processor?

Except experiencing the new features and power consumption techniques has added to the new processors, If your device runs under 4GB of RAM, you don't need a 64bit CPU. 32bit processor normally provides them with enough performance and memory access. So, should we upgrade?

In brief, Except that It's limitation of the accessible memory, there's no any other significant differences in between 32bit and 64bit architecture. Except for other extra added features.