Machine
omega reaches the hardware through ordinary words, and this page lists them by group. Everything runs in ring 0, so you can poke anything you want and you can also fuck up the whole machine doing it.
peek and poke accept any address, and memmap lists what is at which address (look before you poke).
Memory
The memory words are peek poke peekd poked peekq pokeq alloc free heap.
memmap lists what is at which address.
Ports and processor
The words for I/O ports and the processor are in out ind outd pci pci@ cpuid cpu cr rdtsc irq. in and out accept any port, so don't be a dumbass about it.
Time
The time words are ticks hz time idle stats sleep rand.
Screen
The screen words are put text screen@ wipe cursor nocursor where size title tab mytab.
cursor takes arguments and is not a word that shows the cursor. nocursor hides it. The screen is 80x25 VGA text, and Internals has the details.
Machine and disk
The words for the machine itself are memmap sys-c reboot halt. The words for disks are drives disks install install-to save home, and Installation explains install.
Programs
The inspectors pcils, memls and cpuinfo are in root/30-inspect.om and you can read them with 'pcils open.