[TUHS] PDP-11 questions

Ok, I got a few questions about PDP-11. First, I was wondering when Bell Labs got that first PDP-11/20 what software (if any) came with it? I assume when one bought a PDP-11/20 you would get some type of OS with it. According to the folks at alt.sys.pdp11 the PDP-11 computer doesn't have anything equivalent to a PC's BIOS. But I know a bit about what a PC's BIOS does and that includes RAM Initialization. Wouldn't the DRAM on the PDP-11/something need to be initialized too? Perhaps an older PDP-11 doesn't have DRAM but surely the later models did? Now the last question has to do with what made the PDP-11 architecture so great. Part of that had to be the relatively affordablility of the PDP-11 and of course it was the machine that made Unix possible. It seems though that there should have been a PDP-11 based desktop and as far as I can tell that didn't happen. Instead we got a bunch of micros with 8080, z80 and 6502 cpus, but nothing that could run Unix, at least not a Unix v7 with source code. Mark