I just discovered https://bbs.archlinux.org/viewtopic.php?id=239672
I will check if clocksource=hpet will make a difference.
Update: Now it stops at the following, waiting for timeout:
Even though you can let it timeout and install, the result on these older CPUs in VirtualBox is not really worth bothering. It looks like this has been known for some time and patches exist, but Beta still uses 4.18.0.
FWIW, here are some more updates since I wanted to see what Workstation in Beta 8 looks like:
Start the ISO image and continue with the installation as usual. Simply let the system timeout when hanging. The installation will take some time, but it installs.
The first reboot may work albeit slow. Consecutive restarts, however, won't be able to go into Graphics mode to start Gnome. You need to add "3" to the Grub kernel command line to disable GUI.
Startup will take some time, but show you the login prompt. Login as root and disable the firewall do be able to login using your favorite SSH terminal app.
# systemctl stop firewalld
Download the following to install an updated kernel:
# yum localinstall kernel*
This will take some time while dracut is rebuilding initramfs.
You will notice a graphical boot screen, showing 8 and a spinning wheel.
Select "Insert Guest Additions CD image..." from VirtualBox Devices menu.
Run the installer, entering Root password if needed.
Now you can change the resolution, however, my screen keeps flashing.