Comment by unilynx
7 years ago
The 8086/8088 didn't have that A20 line setting. That was added later for backwards compatibility.
The 80286 reset thing wasn't a full PC reset, but a CPU reset.
7 years ago
The 8086/8088 didn't have that A20 line setting. That was added later for backwards compatibility.
The 80286 reset thing wasn't a full PC reset, but a CPU reset.
> The 8086/8088 didn't have that A20 line setting. That was added later for backwards compatibility.
True
> The 80286 reset thing wasn't a full PC reset, but a CPU reset.
That required an extra hardware and BIOS support. The CPU had to be reset externally, and after jumping to FFFF:0000, the BIOS had to recognize that this is a CPU reset, not re-initialize the hardware and return execution to where it came from.