# The following major new features were added:
* Support for cloning of VMs
* GUI: enhanced wizard for creating new virtual disks
* GUI: new wizard for copying virtual disks
* GUI: keep the aspect ratio in scale mode (Windows and OSX hosts only)
* VMM: raised the memory limit for 64-bit hosts to 1TB
* Experimental support for PCI passthrough for Linux hosts, see Section 9.6, “PCI passthrough”
* Windows guests: Experimental WDDM graphics driver
* Guest Additions: modules and features now are represented as facilities to have a common interface for frontends
* Networking: new network attachment mode "Generic Driver", which offers an open plugin architecture for arbitrary and separately distributable virtual network implementations
* New Networking Mode UDP Tunnel: allows to interconnect VMs running on different hosts easily and transparently, see Section 6.2, “Introduction to networking modes”
* Experimental support for SATA hotplug added. Currently only supported for hard disks and only with VBoxManage.
* Solaris hosts: New Crossbow based bridged networking driver for Solaris 11 hosts (build 159 and above).
# In addition, the following items were fixed and/or added:
* VMM: more SMP timer fixes
* VMM: fixed sporadic recompiler crashes with SMP guests
* VMM: many small fixes
* GUI: when reverting to a snapshot, ask for taking a snapshot of the current state
* GUI: added a View menu
* GUI: added a setting for the promiscuous mode policy for internal networks, bridged networks and host-only networks
* GUI: the VM description is editable during the runtime of a VM
* GUI: added proxy settings
* GUI: made the number of SATA ports configurable
* GUI: decrease time before showing the VM configuration dialog
* VBoxManage: more convenient configuration of storage controller attachments by automatically determining the port or device parameter when a storage controller has only one port or device per port
* VBoxManage: changed syntax of the guestcontrol command group, fixed various bugs, removed obsolete options
* VBoxBalloonCtrl: new service for automatic dynamic adjustment of the balloon size for running VMs
* Settings: machine names and snapshot names are not allowed to be a valid UUID
* Settings: provide better diagnostics if a single medium is used twice in a VM configuration
* Settings: provide better diagnostics for errors in medium create/merge/clone operations, and fix memory leaks in error cases
* Storage: ATA/SATA drives can be marked as non-rotational, i.e. the guest OS will detect them as a SSD if supported, which can improve performance
* Storage: virtual CD/DVD images will be detached if the guest ejects the medium, unless the drive is marked to handle ejects only on a temporary basis
* Storage: the medium UUID can be changed again when attaching a medium for the first time, which allows using images which are exact duplicates including the UUID
* Storage: fixed possible data corruption under certain circumstances with VHD and Parallels images
* Storage: fixed unnecessary expansion when cloning differential images in VDI format
* Storage: fixed detection code to handle empty files for VDI and VMDK format
* Storage: fixed access to CD/DVD images beyond 4GB when using the SATA controller
* Floppy: several bugs have been fixed
* Floppy: make it possible to unmount a host floppy disk
* BIOS: disk-related structures are now checksummed correctly
* USB: many fixes for the Windows USB host driver
* NAT: reduced memory footprint
* Networking: fixed the problem with segmentation offloading when several VMs are transmitting in parallel
* Networking: workaround for a bug in wireshark when operating directly on a capture file created by VirtualBox
* Serial: announce the serial devices in the ACPI tables to make Windows guests find the virtual hardware
* VRDP: support for TLS connections
* VRDP: support for multimonitor client configurations with MS RDP clients
* 3D support: fixed GL_VERSION string for different locales
* Webservice: fixed timeout handling with HTTP 1.1 keepalive, and be more robust when connections fail
* VBoxSVC: fixed regression when several clients trigger autostart simultaneously
* Main: fixed incorrect handling of the medium location for media which are not file based (e.g. iSCSI), which resulted in confusing location values in many places
* JAX-WS client bindings: fixed resource leak
* Sources: fixed USB 2.0 support using extension packs for non-official builds
* Mac OS X hosts: fixed non-VT-x mode on Lion hosts
* Windows hosts: fixed copy'n'paste in the GUI and for the VM window
* Windows hosts (64-bit only): enabled removing of all mediums when removing a VM
* Windows hosts (64-bit only): enabled live snapshot deletion
* Solaris hosts: fixed preemption issue with Solaris 11 hosts (builds 166 and above)
* Guest Additions: improved driver installation on Windows guests
* Guest Additions: fixed high CPU usage while executing guest programs from the host
* Solaris Additions: fixed automounting of shared folders