1. Forum
  2. Usenet
  3. COMP.OS.CPM

  • Z80 vs 8088 speed

    From Nils M Holm@21:1/5 to All on Sun Nov 12 17:26:09 2023
    Just compiled my T3X/0 compiler on an 8088 @ 4.77 MHz under DOS
    and was surprised to see that it takes only slightly less time
    than on an Z80 @ 4MHz under CP/M. See http://t3x.org/t3x/t3x0.html

    I would have guessed that the 8088 is much faster at about
    the same clock speed, because it has more 16-bit operations
    and does multiplication and division in hardware. Of course
    the compiler back ends also play a role, but the Z80 backend
    typically emits *more* instructions for the same program.

    I have never used an 8088 back in the days. In case you have,
    what was your experience? Any technical explanation for my
    results?

    --
    Nils M Holm < n m h @ t 3 x . o r g > http://t3x.org

    --- SoupGate-Win32 v1.05
    * Origin: fsxNet Usenet Gateway (21:1/5)
  • From Dennis Boone@21:1/5 to All on Sun Nov 12 19:23:08 2023
    I would have guessed that the 8088 is much faster at about
    the same clock speed, because it has more 16-bit operations
    and does multiplication and division in hardware. Of course
    the compiler back ends also play a role, but the Z80 backend
    typically emits *more* instructions for the same program.

    The 8088 gives up a substantial portion of any 16-bit advantage to its
    8-bit external bus.

    De

    --- SoupGate-Win32 v1.05
    * Origin: fsxNet Usenet Gateway (21:1/5)
  • From Zbig@21:1/5 to All on Sat Nov 18 04:25:49 2023
    The 8088 gives up a substantial portion of any 16-bit advantage to its
    8-bit external bus.

    Not just that: https://trixter.oldskool.org/2011/06/04/at-a-disadvantage/

    Quick, without doing any research: What early 1980s computer was faster,
    the IBM PC or the Commodore 64? The IBM PC ran an 8088 at nearly 5MHz,
    whereas the C64 ran a 6502 variant at 1MHz. The PC cost thousands of dollars, the C64 hundreds. The PC had a 1 megabyte address space; the C64 only 64K.
    Is this a trick question?

    It is! The C64 was faster. [..]

    --- SoupGate-Win32 v1.05
    * Origin: fsxNet Usenet Gateway (21:1/5)
  • From Nils M Holm@21:1/5 to Zbig on Sun Nov 19 11:41:47 2023
    Zbig <[email protected]> wrote:
    The 8088 gives up a substantial portion of any 16-bit advantage to its
    8-bit external bus.

    Not just that: https://trixter.oldskool.org/2011/06/04/at-a-disadvantage/

    Quick, without doing any research: What early 1980s computer was faster,
    the IBM PC or the Commodore 64? The IBM PC ran an 8088 at nearly 5MHz, whereas the C64 ran a 6502 variant at 1MHz. The PC cost thousands of dollars, the C64 hundreds. The PC had a 1 megabyte address space; the C64 only 64K.
    Is this a trick question?

    It is! The C64 was faster. [..]

    Interesting! So the real surprise is that the 8088 at about the same
    clock speed is almost as fast as the Z80.

    --
    Nils M Holm < n m h @ t 3 x . o r g > http://t3x.org

    --- SoupGate-Win32 v1.05
    * Origin: fsxNet Usenet Gateway (21:1/5)