[cctalk] Re: 80386 - 1985

On Wed, Aug 06, 2025 at 06:26:44PM -0700, Fred Cisin via cctalk wrote: I have no love for the x86 architecture, but note that the 80286 did succeed at what we can safely assume was the design brief: improve on the 8086, and add a protected mode. That it's not a very efficient protected mode is an rather unfortunate design mis-step which still dogs x86 to this day, but if you pretend that feature doesn't exist and leave the CPU in real mode than you get a very welcome performance boost. I would perhaps go further and note that it delivered a technically useful protected mode in 1982, before my personal favourite architecture of that era, m68k. The MC68451 external MMU *added* base-and-bounds segmentation to m68k which seems to date from 1983 (in as much as the oldest datasheet is from April 1983) and of course ideally also needed to be paired with at least the 68010 rather than the 68000 which couldn't restart instructions. That we forget the MC68451 exists shows what a dead-end base-and-bounds was even back then. Wikipedia claims the following, which explains Gates' attitude: 'Bill Gates referred to the 80286 as a "brain-damaged" chip, because it cannot use virtual machines to multitask multiple MS-DOS applications[22] with an operating system like Microsoft Windows.' In other words, he didn't like it because it didn't provide a feature that he wanted for Microsoft. Well, tough, you should have been working with Intel instead of just freeloading. I mean, look at the complexity with base-and-bounds, rings, and all that other arcane stuff which looks like mainframes rather than microprocessors. Protected mode was clearly designed with IBM rather than Microsoft in mind. That was partly a mis-step, but again it was understandable when you consider who the actual customer was. Look at PC operating systems today, and you'll see that they switch into long mode in early startup and stay there until reboot.