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Author Topic: Can i8088 run i8086 8-bit code and vice versa?  (Read 168 times)

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MIRKOSOFT

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    Can i8088 run i8086 8-bit code and vice versa?
    « on: January 10, 2019, 05:20:39 PM »
    Hi!

    This Q looks crazy, but I found not yet enough resources to get answer.

    So:
    i8088 is 8-bit CPU and was used in old XTs or PCjr.
    i8086 is 16-bit CPU and I think it is possible to write 8-bit program 'cause x86 assembler allows to use registers in 32/16 and 8-bit size by instructions.

    But if was 8-bit software written for i8086 will it work on machine with i8088?
    And 8-bit program written for i8088 will run on machine with i8086?

    All these Qs are also for CPU architecture - x86 we all know... but what architecture can be applicable on i8088? Is is totally other CPU or can be marked as x86, even if is only 8-bit?

    Thank you for explaining all.
    Miro

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    Re: Can i8088 run i8086 8-bit code and vice versa?
    « Reply #1 on: January 10, 2019, 06:32:27 PM »
    i8088 is 8-bit CPU and was used in old XTs or PCjr.
    the 8088 is a 16-bit CPU. It uses an 8-bit data bus which affects it's performance but has nothing to do with the instructions it executes. It executes exactly the same instructions as the 8086, but slightly slower due to the 8-bit data bus.

    For comparison, the 80386SX is a 32-bit CPU even though it only has a 16-bit data bus.

    I was trying to dereference Null Pointers before it was cool.

    MIRKOSOFT

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      Re: Can i8088 run i8086 8-bit code and vice versa?
      « Reply #2 on: January 10, 2019, 06:38:39 PM »
      Thank you for explaining.

      You helped me very.

      Miro

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      Re: Can i8088 run i8086 8-bit code and vice versa?
      « Reply #3 on: January 10, 2019, 06:46:56 PM »
      the 8088 is a 16-bit CPU. It uses an 8-bit data bus which affects it's performance but has nothing to do with the instructions it executes. It executes exactly the same instructions as the 8086, but slightly slower due to the 8-bit data bus.

      For comparison, the 80386SX is a 32-bit CPU even though it only has a 16-bit data bus.
      That is right.  But some research will show the intent was to make a cheaper CPU. It was not about making another  change to the instruction set.
      Reference:
      https://en.wikipedia.org/wiki/Intel_80386
      Quote
      In May 2006, Intel announced that 80386 production would stop at the end of September 2007.[9] Although it had long been obsolete as a personal computer CPU, Intel and others had continued making the chip for embedded systems. Such systems using an 80386 or one of many derivatives are common in aerospace technology and electronic musical instruments, among others. Some mobile phones also used (later fully static CMOS variants of) the 80386 processor, such as BlackBerry 950[10] and Nokia 9000 Communicator.
      ...
      Chief architect in the development of the 80386 was John H. Crawford.[11] He was responsible for extending the 80286 architecture and instruction set to 32-bit, and then led the microprogram development for the 80386 chip.

      The 80486 and P5 Pentium line of processors were descendants of the 80386 design.
       
      Fun facts you can use at you net LAM party.  ;D

      Shandy



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        Re: Can i8088 run i8086 8-bit code and vice versa?
        « Reply #4 on: January 11, 2019, 05:31:40 AM »
        That LAM party sure sounds like it'll be a blast