Re: [Qemu-devel] Re: Question about KVM and PC speaker

[Jan Kiszka]

Sebastian Herbszt wrote:
> Jan Kiszka wrote:
>> Sebastian Herbszt wrote:
>>> Simon Bienlein wrote:
>>>> Is a support for BIOS worked on right now?
>>>
>>> The vgabios (vgabios.c) has a "FIXME should beep". Volker, do you plan
>>> to fix this?
>>>
>>> Which frequency should be used for the beep? Which delay?
>>
>> I would try 1 KHz and some hundred milliseconds.
> 
> I just looked at some vga bios and it uses about 896,45 Hz.
> 
>>> Getting a delay using "inb(0x61) & 0x10" is still a no go on qemu,
>>> right?
>>
>> Looks like (should be far too inaccurate for longer delays). What about
>> 0x40:0x6c, the BIOS' daily timer counter?
> 
> The bios i looked at used the refresh request port 0x61. This is
> supported by bochs and
> there is also a patch for qemu to replace the dummy [1]. The rombios
> uses this to provide
> INT 15h AH=86h functionality; this is likely broken with the dummy code
> in qemu.

I see no problem with improving qemu's emulation accuracy this way a
bit. But I wouldn't built new delay implementations on top of it,
specifically if the code is in fact aware of running over a hypervisor.
Such micro-timings are far too inaccurate for longer delays in an
environment where you cannot be sure of running all the time during that
period.

> 
> Anyway, using "timer ticks since midnight" should be possible (INT 08h
> handler is set up
> before vga bios is called).
> 
> [1] http://article.gmane.org/gmane.comp.emulators.bochs.devel/7594
> 
> - Sebastian
> 

Jan

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