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