|
|
|
|
|
|
by Zuider
1114 days ago
|
|
|
It is a kernel/OS level concept (though it was also used in games.) Historically, task-switching had hardware support to some degree even in 8-bit microprocessors such as the Z80, M6809, and 6502 and in 16-bit microprocessors prior to the 386, using interrupts to push all the registers onto a stack, and setting the program counter to start executing instructions at a new address. The vital innovation introduced with the 386 was to add memory protection, so that the different tasks could not corrupt each other's allocated memory. Hitherto, multitasking was too unstable for serious commercial use. |
|
|
however, hardware memory protection was an innovation of the early 01960s; it featured prominently in designs like the burroughs 5000 (01961), the ferranti atlas (01962), the cdc 6600 (01964), and the ibm 360 model 67 (01965)
but the 80386 didn't ship until 01985, at which point hardware memory protection had been in off-the-shelf commercial computers for 24 years, very much in serious commercial use; in particular, most of the internet ran on pdp-10s, pdp-11s, vax-11s, and sun workstations, which all had memory protection. it had become universal in mainframes and almost so in minis during the 01970s, and even some micros like the lsi-11 and suns had it
the 286 also had memory protection. what it lacked (like the pdp-11, including the lsi-11) was 32-bit registers. the 386's 32-bit register set meant you didn't have to use segmentation, which was a huge problem for 286 protected mode, and linux mostly doesn't