alina @alina@chaos.social

Unless you were there, you really cannot appreciate how much damage Intel did to the PC ecosystem with the 286.

https://en.wikipedia.org/wiki/Intel_80286

The 286 was the successor to the 8086 and 8088 CPUs that powered the original IBM PCs. It offered a huge step forward from them.

Those older chips always ran in "real mode," where memory locations had fixed addresses, and any running program could modify the contents of any address. This meant that you couldn't have two programs running at once, because one might try to use a bit of memory the other was already using, and blammo!

The 286 introduced "protected mode," which prevented programs from being able to mess with memory allocated to other programs. Instead of addresses corresponding directly to blocks of memory, in protected mode they were treated as "virtual" addresses, and mapped to memory allocated just for that program.

Protected mode meant the days when one program could reach into another one and mess with its memory would be over. And that opened up all sorts of possibilities. You could have real multitasking! A whole range of crash bugs would be instantly eliminated! Suddenly the PC began to look like a machine that you could put against a UNIX workstation with a straight face.

But there was a problem. To maintain backwards compatibility with the old chips, the 286 had to boot into real mode. It could then shift into protected mode on demand. But -- and this is a big BUT -- once it was shifted into protected mode, IT COULD NOT SHIFT BACK. The only way to get back into real mode was to reboot the PC.

Which was a problem, because every PC user owned a huge library of DOS software, much of which could only run in real mode. So the 286 gave you multitasking -- but if you ever needed to run a real-mode program, you had to reboot your PC (and lose all the other running programs) to run it.

This was, as you may imagine, not ideal.