Comment 4 for bug 1840719

And the (SeaBIOS) winner is...

4a6dbcea3e412fe12effa2f812f50dd7eae90955 is the first bad commit
commit 4a6dbcea3e412fe12effa2f812f50dd7eae90955
Author: Nikolay Nikolov <email 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.