Pick a ka655x.bin ROM and an ODS-2 .dsk image, then press Start. (Or open this page with ?rom=URL&diskgz=URL to fetch both -- no picker needed.) The disk is read lazily, 64 KB at a time, and is never modified: writes land in an in-memory copy-on-write overlay. Click this screen to give it the keyboard. A boot to the OpenVMS login prompt is a few hundred million instructions and takes a couple of minutes; output streams as it goes.
Click the screen to type. Backspace sends DEL (VMS rubout); Ctrl-key combinations are sent as control characters.