Setup sharepoint 2013 preview in hyper-V encountered an error during setup

I was installing the SharePoint 2013 preview in windows 8 hyper-V environment.
Firstly, it looks good, it is running installing until the last 10% bit,



I am keep getting the unexpected error,

Tried all sorts of ways, such as install all latest update,  run set up as administrator, install office. No matter what, it just can not complete the setup.

The magic to fix it is to modify the virtual machine settings and give 4 virtual CPUs, then it worked !