just use a displayport to vga adapter, displayport is almost made to work with all standards, HDMI isn't.
How can I use my existing display or digital TV set with a new computer that has a DisplayPort output?
A. DisplayPort has the unique ability to support external display adapters. The DisplayPort Source device (such as a notebook computer) provides power at the DisplayPort plug to power such an adapter, and it detects the type of adapter connected, as well as the type of monitor. Inexpensive DisplayPort adapters are readily available for VGA, DVI, and HDMI displays. Adapters for HDMI 2.0 will become available in the near future.