5 ms·
Author here. I'm without electricity but can discuss the 8086 if anyone has questions :-)
by kens 4y ago
Author here. I'm without electricity but can discuss the 8086 if anyone has questions :-)
- jzwinck 4y agoAs far as I know, x86 and x86-64 have never had microcode for ASCII (base 10 is what I'm interested in) to binary number conversion. Why do you think this is? It seems like a very common operation these days, and the reasons you gave for microcode multiply seem applicable.
- kens 4y agoThe IBM System/360 (1964) had instructions to convert a character string to packed decimal, and to convert packed decimal to binary. This was motivated by the large amount of punch-card data that was handled back then, with all the numbers in decimal. But I guess Intel figured that string conversion wasn't common enough in modern systems to merit adding it to the instruction set.
- prirun 4y agoPrime minicomputers had decimal arithmetic in microcode & hardware in the early 80's to support PL/I and COBOL "picture" data types and packed decimal. They also had sophisticated editing to pictures like ZZZ,ZZ9.99 which would display 1024 as 1,024.00 These instructions were also implemented in PMA, the Prime Macro Assembler, in the OS so that if a machine didn't have these instructions, a UII fault occurred and the instruction was simulated in software. I implemented a lot of the easier instructions in C in the Prime emulator, but for the more complex things like decimal math, I let those fault so the Prime OS would handle them.
- detrites 4y agoNot a question, just a comment that after having read several of your posts now, building up knowledge as I go, this one is the first I've understood from start to end. Most satisfying!
- gregschlom 4y agoKen, I've read and enjoyed many of your posts and I always wonder: how do you find so much time to do that? Is that your full time occupation? Thanks!
- kens 4y agoI'm retired, so I have time for various vintage computer projects.
- peteri 4y agoInteresting, any reason for not discussing AAD yet? (oh and great series BTW)
- kens 4y agoAAD is lower on the list since it is both complicated and kind of obscure. Also, it depends on multiplication and division, so I want to cover them first.
- bonzini 4y agoAAD is essentially a multiplication and a sum: 170 Q -> tmpc 171 AH -> tmpb CALL CORX 172 AL -> tmpb ADD tmpc 173 ZERO -> AH JMP 179 179 SIGMA -> AL RNI F It doesn't depend on division despite the name, it performs ASCII to binary conversion.
- johndmcmaster 4y agoWhat is your favorite BBQ sauce to pair with an 8086?
- kens 4y agoI think the Fairchild Microflame works better for barbecue :-) https://en.wikipedia.org/wiki/Fairchild_9440 https://en.wikipedia.org/wiki/Fairchild_9440