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

From: Sebastian Herbszt
Subject: Re: [Qemu-devel] Re: Question about KVM and PC speaker
Date: Sun, 10 May 2009 00:21:27 +0200

Jan Kiszka wrote:
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,

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

Volker, mind to resubmit the patch once again?

Anyway, using "timer ticks since midnight" should be possible (INT 08h
handler is set up
before vga bios is called).

I have implemented the beep for vgabios-6b and it works on bochs but fails on 
With "-soundhw pcspk" i should hear it thru the hosts pc speaker, right?

- Sebastian

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