32 bit vs 64 bit Comparison

The fact is that the /3G switch won't change how many system memory can be addressed/accounted for globally.

Yes by defining /3G at system start up will increase the user space memory from 2 GB to 3 GB. But don't forget that this "user-mode virtual address space" is using the "global pool" of RAM that is addressable by the kernel. It still remains that the limit of memory you can "have" on a 32bit OS is still around 3GB. Depending on how many devices you have on your system, addressable memory count will go down along with increased device installed and vice versa.

Lordbob75, I think you should include our little chat over PM to the main thread. It will clear a lot of confusions.

zzz2496.

zzz2496 said:

I see... OK, wipe the slate clean. Let's go back to basics... I think I lead you to the wrong idea, I'll explain it in numbers this time...

Every device in our computer needs to have an address. The addresses for those devices are defined in hexadecimal format: 0x00000000 up to 0xFFFFFFFF in 32bit system (16^8 = 2^32). For a computer to be able to use a device, first it needs to make sure it's known - by giving it an address number (a 0xYYYYZZZZ number). This number is not related to your RAM, it's an independent value.

32bits processors understands 4.294.967.296 addresses: 0x00000000 up to 0xFFFFFFFF (2^32). This is the max for 32bit systems. Now let's say your have 4GB of RAM, you need to address every byte of it, which will require 4.294.967.296 addresses, this can't be, because the limit is 0xFFFFFFFF (4.294.967.296 in hexadecimal), so the system will reserve every device it found in your system on the lower part of the address space thus will abandon your RAM in the process. Let's say your devices use 0x00000000 to 0x2FFFFFFF (1.073.741.824) addresses.
Your RAM's address will have to start at 0x30000000 up to 0xFFFFFFFF (3.489.660.927 addressable RAM - RAM is calculated in bytes, thus 3.489.660.927 bytes). If you have 4.294.967.296 worth of RAM, your processor can't address the rest of your RAM (805.306.369 bytes), because it ran out of 32bit address space.

In 64bit systems you can have as much as 0x0000000000000000 up to 0xFFFFFFFFFFFFFFFF or 18.446.744.073.709.551.616 addresses, this is exactly 4.294.967.296 TIMES LARGER address space than 32bit systems (2^64). Let's say your devices uses 0x0000000000000000 up to 0x000000002FFFFFFF (which is 1.073.741.822 addresses), that will leave 18.446.744.072.635.809.794 addresses to use... Your devices addresses ends at 0x000000002FFFFFFF, your RAM will start at 0x0000000030000000 address ends at 0x0000000130000000. As you can see, the address space in 64bit processor still leaves a lot of room to expand.

I hope this clears the address reservation issue...

zzz2496

Hope this helps.

~Lordbob

Very usefull article,for which thanks.:)

Now i do have a question.(i hope this wasn't asked already,if so i do apologize)

How about OEM licenses,i do have an installation dvd with only (??) the 64 bit edition.
Now could i use the same key to install a 32bit version???
I build my pc myself,hence the oem-systembuilder license,which is also a lot cheaper (+- 50%)

It's just something i would like to know,i defenitly will stick to the much superiour 64bit-version of win 7,but a lot of people asked me this???

I hope you or someone else might know.
Thanks in advance

alfranatic said:

Very usefull article,for which thanks.:)

Now i do have a question.(i hope this wasn't asked already,if so i do apologize)

How about OEM licenses,i do have an installation dvd with only (??) the 64 bit edition.
Now could i use the same key to install a 32bit version???
I build my pc myself,hence the oem-systembuilder license,which is also a lot cheaper (+- 50%)

It's just something i would like to know,i defenitly will stick to the much superiour 64bit-version of win 7,but a lot of people asked me this???

I hope you or someone else might know.
Thanks in advance

You're welcome. The license key will work for both x32 and x64 versions. The restriction is on the version of Windows, such as Home Premium, Pro, and Ultimate.

~Lordbob

Thanks,Lordbob for your swift and clear answer.

alfranatic said:

Thanks,Lordbob for your swift and clear answer.

No problem. Glad to help.

~Lordbob

blondie91702 said:

This is great info! My system came pre-installed by Best Buy Geek squad ... does that mean, if I wanted to, I could reformat and choose to use x32? Also, did not see anything about the x86 ... I have two sets of program files it seems... one says Programs x86 ?

Ugh, Geek Squad...

Yes, you can install either x32 or x64 with the same key, as long as it is the same version (ie Home Premium, Pro, Ultimate).
Also, the Program Files x86 is the directory most programs will install to if they are not native x64, and this is perfectly normal.

~Lordbob