The inclusion of Hyper-V in Windows 8 Pro and Windows 8 Enterprise was a huge benefit for those of us who work in environments where Hyper-V is the hypervisor of choice, which I guess also includes those of us who use Azure IaaS capabilities. Being able to build dev and test VMs on your desktop, laptop or tablet, and then move them over to a high performance server without making changes is something that I take advantage of every week, so I definitely see the benefits.
With the updated Hyper-V in Windows 8.1 Pro, one of the new capabilities is the Generation 2 virtual machines, which provide a number of benefits, but for me the big improvement is being able to do PXE installs into a VM at greater than 100Mb/s speeds, which is a common scenario for me and one that frustrates me for two two reasons. First of all, the deployment is slower, but the second one is the need to remember to remove the legacy adapter after the VM is created.
Let’s take a look at what is required to create Gen 2 VM, and then take a look at some of the differences between Gen 1 and Gen 2 VMs.
No major differences at the start of the new VM wizard.
Again, the options are what you are used to.
Now we see a difference – and the Gen2 option lists some of the features, as well as the requirements for Windows 8 or Windows Server 2012 or higher, 64 bit editions or higher.
From there it’s back to the familiar wizard
Choosing a network UI hasn’t changed.
No VHD creation UI changes to note.
No surprises here.
And the summary screen hasn’t changed much either, but it does give a final chance to notice that I did select a Gen2 VM.
Selecting a Gen 2 VM does have an impact on the settings of the VM, so let’s compare the two.
First of all you can see that we only have three choices for add new hardware. 
In the legacy machine we see the extra option for Legacy Network Adapter, which is needed in Gen1 VMs to support PXE.
Next up we can see that there is a new option for Firmware, in which we can change boot options which supports Secure Boot.
This is another screenshot of the Gen2 VM after Windows 8.1 Enterprise 64 bit has been installed as the guest OS, and you can now see that the Windows Boot Manager has kicked in.
Gen1 VMs present a different list of boot devices.
As we look at the storage options, we are only presented with SCSI based HDD or DVD in Gen2 VMs. One of the important changes here is that SCSI boot is now supported, so the legacy IDE adapter can be retired.
As you can see above, the Gen1 VMs rely on the emulated IDE controller for boot capabilities.
To wrap up today’s post, you need to consider the VM portability when you go down the Gen2 path, as it isn’t backwards compatible with older versions of Hyper-V. In the next post I will cover more of the differences, as well as their impact in more detail.