What is the difference between x86_64 amd64 and 64 bit?

Question

I use a x86_64 bit Ubuntu, but whenever I try to do a live boot of any other 64 bit images like the GNOME 3.16 which was released yesterday, it does not work?

Also some times when I try a virtual machine of a 64 bit image, it does not work either.

What is the reason for the same? What is the difference between x86_64 amd64 and 64 bit?

My laptop model is an Hp Pavillion dv4 1506tx. The processor is 2.20 GHz Intel Core 2 Duo Processor T6600

Solution 1

This may not solve exact problem, but I'll clarify the difference between x86_64, amd64 and 64-bit.

Every micro-processor implements an instruction set (also called instruction set architecture or ISA in short).

64-bit ISA or 64-bit processor that the length of address bus is 64 bits. Intel/AMD have variable length instructions - they vary from 1byte to 15 bytes. So, instruction length does not determine what type(32/64-bit) processor it is.

x86_64 is name of specific 64-bit ISA. This instruction set was released in 1999 by AMD (Advanced Micro Devices). AMD later rebranded it to amd64.

Other 64-bit ISA different from x86_64 is IA-64 (released by Intel in 1999).

Solution 2

Actually... AMD64 is the real 64 bits architecture that AMD created and intel licensed it and uses it even today (just as AMD had the license to use x86 on the 32 bit CPUs). x86_64 far as i know is nothing more than a 32 bit CPU that can address the extra memory that a supposed 64 bit system need (so like a 32 bit system that recognizes and uses more than 4GB of RAM).

Comments

[Thomas Ward]

How is this different from the existing answer?

[MariusM]

No, x86_64 is the real 64bit architecture. You are conflating it with i686 PAE (physical address extension implemented using virtual memory tables of operating system) which extends memory support beyond 32bit memory space (beyond 4GB).

[tinmac]

+1 Also CPU's have a Data bus and an Address bus - both are 64 bit in x86_64 (aka amd64). Intel Pentium 32 bit refers to the Address bus hence 4GB physical memory limit but it employed a 64 bit Data bus.

[scarface_90]

x86 is a family of instruction set architectures, and it has different bits like 16-bit, 32-bit, and 64-bit. So I think you are wrong about 32bit. FMI please check this link

[Philip Couling]

+1 because I'd always thought it named amd64 first but it seems AMD themselves branded it (with trademark) as "AMD x86-64". See here and here

[David]

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