AlphaVM does not actually emulate OpenVMS. AlphaVM emulates the DEC Alpha system hardware. As the result OpenVMS runs on the virtual hardware unmodified. Since the emulated hardware is Alpha, it is OpenVMS/AXP that runs on AlphaVM.
In fact, for the user it may look like OpenVMS runs on the Intel x86-64 based hardware. AlphaVM is a software layer that makes it possible.
The performance of such emulation is adequate for most applications. Most workloads are faster on AlphaVM than on the real Alpha system provided that the host hardware is fast.
AlphaVM is designed to replace systems running OpenVMS and save the costs associated with the electricity bills, support and maintenance. It allows to run old software unmodified with no risks of old hardware failures.
AlphaVM-Pro can be used to replace Alpha systems (AlphaServer or AlphaStation) of all kinds. The faster systems like DS25 or ES47 also can be replaced with adequate performance. For such fast systems one has to choose the host hardware with high clock speed.