yep, the 1600's and the other lower-profile processors- remember the 44xx series of 4 bit 'cpu's'?- (yes, I agree that entering machine code by hand, flipping switches on the front panel, double checking, punching the 'set location and increment address' switch, then repeat till your fingers fell off... even just a bootloader and then starting the paper tape through the teletype 33 well and truly s*cked- and poking and peeking via rom basic wasn't fun- and by then you could actually save and restore from audio tape, ooh! dos was a dream come true in some ways, but I still think vista is a step too far unless you can afford a new computer or have to buy one- and then I'd prefer a downgrade just because I hate being on the bleeding-out-edge.) were the chinese curse kind of fun. I ran into them- painfully- several places.
OTOH, I once found a half a ton of prototype commercial kitchen timers at a northern california metal scrap yard- 453 of them- each with 6- 0.3" socketed 7-segment led displays and a socketed 8085 cpu with on-die uveprom.
bought the lot for the weight of stainless steel scrap (the cases- $2 a pound- <grin>), then ran them 350 miles down to Mike Quinn's electronic surplus in Oakland and turned them over to Mike (for the cpu's alone- tossed the rest in for his labor pulling the boards out) for a profit after gas of $2.83 each. sweet time.
I barely brushed against MP/M, barely got introduced before I ended up running a video arcade and doubling as a soda jerk for several years- I do have an S-100 system with Oasis 8-bit and a 20 meg 8" fujitsu hdd stored here, though. IIRC it's related in places. I rather liked IBM PC-DOS 7 multiuser running remote serial terminals, brought back memories.
"Machines, large and small, ran one program at a time"- ohyeah- one *small* program, *slowly*. 4k memory upgrades *hurt*.
well, mainframes like the Honeywell 6000 series I trained on the year before the micros showed up (1976, that is- I think it was 24 or 36 bit- the DEC PDP-8L mini in the classroom was 12 bit & I still have the core memory- wish I had that line printer!) sure time-shared like a bandit- for the time.
it was right painful porting a BASIC program over to the 8080 micro, making it fit- and then seeing how slooooow it ran.
The athlon xp in the other room could kick the H-6000's bits in most categories but power draw... you could run this *town* on the output from the UPS multiple motor-generator sets that kept it on-line.
come to think of it, I may still have a video game X-Y monitor that used one of that class cpu to translate the digital input into sweep commands. Armor Attack 19" b-w.