On 4/21/22 15:14, Fred Cisin via cctalk wrote: > On Thu, 21 Apr 2022, Mike Katz via cctalk wrote:>> Intel has never understood > interrupts or good cpu architecture. >> Look at the segment:offset architecture of the 8086 and of course it's >> single interrupt (without the separate interrupt controller chip) vs >> the 68000 somewhat orthogonal 32 bit architecture and 256 interrupts >> with 8 levels built into the chip. >> I could spend pages just describing how the 68K chip just blows away >> the 8086 considering they were both released at about the same time. >> For crying out loud the 6809 even though it only addresses 64K is a >> more powerful processor than the 8086. Even with the 8086 clocking >> faster than the 6809.
A lot of it was a matter of "Vass you dere, Shollie?" To be fair, how to do 8-level interrupts with the 8080 and 8008 was detailed in several application notes and provided initially by the 8214 PICU; before that, schematics were published on how to use the 74148 priority encoder. It's noteworthy that the 8085 included an on-chip priority encoder, as did the 80186. Initially, the 8086 was never really intended to be in the same target market as the 68K. Intel had the iAPX 432 plans for that--the so-called "micro mainframe". One thing that Intel did offer was a rich range of support chips--something that was a concern for early potential adopters of the 68K. What Intel did realize is that, like it or not, backward compatibility is very important. Much of the early IBM PC software was converted 8080 assembly language--Intel even provided a conversion tool. Given the expense of developing new software back then, that was a big concern. Heck, even PC-DOS was a loose rehash of CP/M-80 with a different filesystem stapled on. The compatibility lesson came back to haunt Intel recently with the IA64 (Itanium) architecture. It should be noted that I really, really liked the architecture of the 68000; in the same vein, I really, really liked that of the NSC 32000 chips. I really liked the PowerPC chips and use ARM MCUs in my embedded stuff. But my desktops still use Intel-compatible CPUs. I'm reminded that almost every car on the road still has a dashboard fixture called a "glove compartment" to keep your driving gloves safe. --Chuck
