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53
zk/Instruction_set_architectures.md
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@ -20,9 +20,9 @@ tags: [CPU]
## Architecture is logical not physical
> Note that this is a logical architecture rather than a physical architecture.
> Like ISA processors may work very differently on the hardware level whilst
> still adhering to the same ISA
The "architecture" of an ISA is logical rather than physical, i.e processors
that share an ISA may work very differently on the hardware level whilst still
adhering to the same instruction set.
## ARM and x86
@ -31,34 +31,37 @@ introduced by Intel but are also made by AMD.
### x86
The name stems from Intel's internal naming conventions - every new processor
they introduced would have a letter designation ending with "86". Later they
would adopt names such as "Pentium", "Celeron" etc. Regardless, these processors
still fall under the "x86" family.
- First introduced by Intel but also made by AMD.
Over time, new instructions have been added to the x86 architecture but they all
maintain backwards compatibility with preceding generations.
- Name stems from Intel's internal naming conventions - every new processor they
introduced would have a letter designation ending with "86". Later they would
adopt names such as "Pentium", "Celeron" etc. Regardless, these processors
still fall under the "x86" family.
There have been different, successive generations of x86 corresponding to their
[word-size](Signed_and_unsigned_numbers.md): 16-bit, 32-bit, 64-bit. Word size
here just means how many bits the processor can work with at a time.
- Over time, new instructions have been added to the x86 architecture but they
all maintain backwards compatibility with preceding generations.
A 34-bit processor can operate on values that are 32 bits in length. This means
it has 32bit [[CPU_architecture#registers|registers]], a 32-bit data
[[Bus|bus]], a 32-bit address bus and so on.
- There have been different, successive generations of x86 corresponding to
their [word-size](Signed_and_unsigned_numbers.md): 16-bit, 32-bit, 64-bit.
Word size here just means how many bits the processor can work with at a time.
A 34-bit processor can operate on values that are 32 bits in length. This
means it has 32bit [[CPU_architecture#registers|registers]], a 32-bit data
[[Bus|bus]], a 32-bit address bus and so on.
AMD introduced the first 64-bit processor, not Intel but they later caught up. A
64-bit x86 processor is often referred to as _x64_ or _x86-64_.
- AMD introduced the first 64-bit processor, not Intel but they later caught up.
A 64-bit x86 processor is often referred to as _x64_ or _x86-64_.
### ARM
Whilst x86 processors dominate the personal computer and server space, on mobile
a different instruction set architecture predominates: ARM. The ARM company
develops the architecture and standard which it licenses it to other companies
to implment.
- x86 processors dominate the personal computer and server space
They are preferred on mobile because they have reduced power consumption and
lower costs compared to x86.
- On movile devices ARM ISA predominates
With ARM processors the processor is on a single chip that contains the CPU as
well as memory and other hardware.
- The ARM company develops the architecture and standard which it licenses it to
other companies to implement.
- Preferred on mobile because they have reduced power consumption and lower
costs compared to x86.
- The processor is on a single chip that contains the CPU as well as memory and
other hardware.