9.4. System Devices
System devices are critical for the guest to run and cannot be removed. Each system device attached to a guest also takes up an available PCI slot. The default system devices are:
- the host bridge,
- the ISA bridge and USB bridge (The USB and ISA bridges are the same device),
- the graphics card (using either the Cirrus or qxl driver), and
- the memory balloon device.
For information about how to use PCI Express and conventional PCI devices with Intel Q35-based virtual machines, see Using PCI Express and Conventional PCI Devices with the Q35 Virtual Machine.