[Qemu-devel] [Bug 1840719] Re: win98se floppy fails to boot with isapc machine

[Philippe Mathieu-Daudé]

And the (SeaBIOS) winner is...

4a6dbcea3e412fe12effa2f812f50dd7eae90955 is the first bad commit
commit 4a6dbcea3e412fe12effa2f812f50dd7eae90955
Author: Nikolay Nikolov <address@hidden>
Date:   Sun Feb 4 17:27:01 2018 +0200

    floppy: Use timer_check() in floppy_wait_irq()
    
    Use timer_check() instead of using floppy_motor_counter in BDA for the
    timeout check in floppy_wait_irq().
    
    The problem with using floppy_motor_counter was that, after it reaches
    0, it immediately stops the floppy motors, which is not what is
    supposed to happen on real hardware. Instead, after a timeout (like in
    the end of every floppy operation, regardless of the result - success,
    timeout or error), the floppy motors must be kept spinning for
    additional 2 seconds (the FLOPPY_MOTOR_TICKS). So, now the
    floppy_motor_counter is initialized to 255 (the max value) in the
    beginning of the floppy operation. For IRQ timeouts, a different
    timeout is used, specified by the new FLOPPY_IRQ_TIMEOUT constant
    (currently set to 5 seconds - a fairly conservative value, but should
    work reliably on most floppies).
    
    After the floppy operation, floppy_drive_pio() resets the
    floppy_motor_counter to 2 seconds (FLOPPY_MOTOR_TICKS).
    
    This is also consistent with what other PC BIOSes do.

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https://bugs.launchpad.net/bugs/1840719

Title:
  win98se floppy fails to boot with isapc machine

Status in QEMU:
  New

Bug description:
  QEMU emulator version 4.1.50 (commit 50d69ee0d)

  floppy image from:
  https://winworldpc.com/download/417d71c2-ae18-c39a-11c3-a4e284a2c3a5

  $ qemu-system-i386 -M isapc -fda Windows\ 98\ Second\ Edition\ Boot.img
  SeaBIOS (version rel-1.12.1-0...)
  Booting from Floppy...
  Boot failed: could not read the boot disk

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