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Old 10-11-2017, 08:00 AM   #1
chrstrbrts
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64-bit Ubuntu seems to contain the 32-bit version as well


Hi,

I'm new and have a basic question.

I burned 32-bit Ubuntu version 16 to a USB and successfully ran it on a 64-bit machine without installing.

This is to be expected as 32 bit Intel code will run on a 64 bit Intel machine as long as you stay in protected mode or go into legacy mode.

I checked the files burned on the USB and saw that under the dists/xenial/main and dists/xenial/restricted folders there is a binary-i386 folder.

This makes sense.

Then, I burned the 64-bit Ubuntu version 16 to a USB.

I checked the files burned on the USB and saw that under the dists/xenial/main and dists/xenial/restricted folders there is a binary-amd64 folder and a binary-i386 folder.

Apparently, the 64-bit version has both the 64-bit code and the 32-bit code.

Why?

What happens if you take the 64-bit version and try to run it on a 32 bit system?

Will the bootloader load the 32-bit version and successfully run the OS?
 
Old 10-11-2017, 08:12 AM   #2
pan64
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the 64bit version cannot run on a 32bit system at all. That is not possible (as far as I know). But you can run both 32bit and 64bit OS on a 64bit system.
 
Old 10-11-2017, 09:30 AM   #3
Rickkkk
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Hi chrstrbrts,

I'm not a Ubuntu user, but I can think of 2 plausible explanations for this:

1) The 64-bit ISO does in fact also contain the 32-bit installer. This would be similar to the case with Arch, the system I use, which for the last couple of years before the discontinuation of the 32-bit version, delivered both versions in the same ISO. This, in my opinion, is the least likely explanation, since if it were the case, there would be no need to continue to deliver two distinct ISOs and Canonical would likely be more specific about their ISO being dual-architecture.

2) The i386 directory you see in the installation package contains specific 32-bit code that may be required for running 32-bit applications on the 64-bit version of the operating system (a fairly common occurrence, although decreasingly so ...). Essentially, these would most likely be 32-bit versions of libraries required by these 32-bit applications.

Voilą - hope this helps.

Cheers !
 
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Old 10-11-2017, 12:18 PM   #4
sundialsvcs
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Exactly ... a 64-bit operating system has to be able to place the processor into 32-bit compatibility mode (or, sometimes, worse ...) in order to run legacy software in the environment that it expects.

A 32-bit OS cannot run 64-bit software, but a 64-bit OS can run both 64-bit and 32-bit software side-by-side. 64-bit applications might need to talk to ("thunk!!") 32-bit libraries. And, so on.

Last edited by sundialsvcs; 10-11-2017 at 12:19 PM.
 
  


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