When IBM developed the PC, they famously chose a bunch of off-the-shelf components. Besides making the machine relatively easy to clone, another effect of this was it used a lot of chips and board space. Consider that a usable IBM PC system with peripherals needed 3 to 4 expansion cards for:
- Video adapter
- Floppy and/or HD controller
- Serial and Parallel ports
Effectively doubling the amount of board space over and above the already large slotted motherboard.
My question is what was the first 100% PC compatible with these basic I/O features built-in on the motherboard? Also, how did they "fit it all" given the legacy of off-the-shelf only components?
NOTE: If the answer is a PC with no ISA slots, then I'd also like to know which was the first that also retained expandability by including some slots.
NOTE 2 (Trying to define "100% compatibility" more pedantically): To my mind, 100% compatibility just means "all the same software media". So the strict requirement is really binary compatibility, and even software that bypasses BIOS and bangs the hardware directly, still works as expected. The secondary requirement would be ISA slots, if it has slots at all, to facilitate off-the-shelf hardware from the general PC expansion card market. So, yeah, you can buy software and hardware for the PC and it works just fine with your 100% compatible clone... This was the standard consumer's aspiration at the time, I think.