#1464 RTC clock is off by 14 minutes with the option "clock: sync=realtime, time0=local"

[Oliver]

I get false readings in the guests system's clock with the setting:

clock: sync=realtime, time0=1"

or

clock: sync=realtime, time0=local"

The guest time is 14 minutes ahead of the host system time.
I get the correct time in the guest systems with the options:

clock: sync=both, time0=local"

or

clock: sync=both, time0=1"

and

clock: sync=slowdown, time0=local"

or

clock: sync=slowdown, time0=1"

I thought the "real time" method would preserve the host-time correlation. However, a deviation of 14 minutes is a very large deviation immediately after starting the emulation. I therefore assume that this is a bug.

https://bochs.sourceforge.io/doc/docbook/user/bochsrc.html#BOCHSOPT-CLOCK

[Volker Ruppert]

Can you please try with the lastest Bochs code from Github?

[Oliver]

I tried it, but bochs fails at the VGA BIOS. See the added txt file.

I compiled it with the following options:

./configure --prefix=/dev/shm/bochs  --enable-debugger --enable-readline --enable-sb16 --with-x11 --with-sdl2 --with-wx 

make
# and
make install

worked without errors.

For the display library i tried both

display_library: x

and

display_library: sdl2

[Volker Ruppert]

You did not set up the vga option, so Bochs uses the VBE extension, but you specify the Cirrus version of SeaVGABios as the vgaromimage. It seems to be unable to boot if there is no Cirrus hardware present. The VGABIOS-lgpl-latest would be the right choice for VBE. If you specify Cirrus as the vga extension, you could also use VGABIOS-lgpl-latest-cirrus.

[Oliver]

Thank you.
This time i recompiled it with:

./configure --prefix=/dev/shm/bochs  --enable-debugger --enable-readline --enable-sb16 --with-x11 --with-sdl2 --with-wx --enable-clgd54xx

It also does run. But the RTC clock is still 11 minutes and 52 s off.
On my host system running linux i have:

20:25

In bochs in my guest OS running Freedos, i have:

C:\>time
Current time is 8:36:52.52 PM.
Enter a new time:
C:\>

[Volker Ruppert]

I cannot see this behavior here.. Please check the initial time in the log file. If the difference is constant, you should see it at startup, too. If the difference is variable, you could try the clock option parameter "rtc_sync=1" to make sure the "one second timer" runs at real #time speed. The clock sync setting only affects the system timer, not automatically the RTC.

[Volker Ruppert]

I'll close this bug report now, since it cannot be reproduced. If it still exists, please create an issue at Bochs project page on Github.