Re: [Qemu-devel] [SeaBIOS] Re: Regression with floppy drive controller

[Gerd Hoffmann]

On Wed, Aug 21, 2019 at 09:31:48AM -0400, Kevin O'Connor wrote:
> On Wed, Aug 21, 2019 at 08:42:08AM +0200, Gerd Hoffmann wrote:
> >   Hi,
> > 
> > > Using the default QEMU config, we build SeaBIOS to use the TSC timer:
> > > 
> > > builds/seabios-128k/.config:CONFIG_TSC_TIMER=y
> > > builds/seabios-256k/.config:CONFIG_TSC_TIMER=y
> > 
> > > Do we need a cpu with TSC support to run SeaBIOS?
> > 
> > Hmm.  seabios uses pmtimer if available.  isapc has no pmtimer though,
> > so it uses TSC instead.
> 
> But, SeaBIOS should have automatically detected no TSC and then fallen
> back to the PIT.  And the check does work correctly with "-cpu 486" in
> my tests.
> 
> Is the PIT not working for some reason in the original setup?  (Any
> time I attempt to run with "-M isapc" I just get an "Unable to unlock
> ram - bridge not found" error.)

Yep, that should be no problem, with isapc the ram is not locked in
the first place.

> The PIT seems to work okay in my
> setup.

Using the floppy image from
  https://winworldpc.com/download/49c380c2-a9c3-af25-c389-11c3a6e28094

qemu-system-x86_64 -cpu 486 -M isapc -fda win98se.raw         => fails
qemu-system-x86_64 -cpu 486,+tsc -M isapc -fda win98se.raw    => works

cheers,
  Gerd