joel@peora.UUCP (Joel Upchurch) (05/08/85)
I have never written assembly language code for any Intel micro- processor, so I was wondering if anyone had an opinion about writing code for the 80*86 versus the IBM 370 architecture. When I used to do systems programming under MVS the base displacement addressing scheme that IBM uses became tiresome very quickly for large programs. Is this better or worse than the problems with segmentation on the 80*86? I thing I can say about IBM's approach it sure encourages modular programming 8-). I'm not talking about the complexities of the operating system, since when it comes to complexity it's hard to beat MVS. If you really want to cure dissatisfaction with 80*86, just try doing some assembler code on the APPLE II sometime. I've come to the con- clusion that the 6502 was invented to punish programmers for sins in a previous incarnation. Joel Upchurch ************ Insert usual disclaimers here ******************* **** IBM, Intel, MVS, and Apple II are probably all trademarks ***
doug@terak.UUCP (Doug Pardee) (05/11/85)
> When I used to do systems programming under MVS the base displacement > addressing scheme that IBM uses became tiresome very quickly for large > programs. Is this better or worse than the problems with segmentation > on the 80*86? The most important difference is that 370 addresses are actually linear. You put an entire address in a register, not part in this register and part in that register. You can pass the address of something around simply. You can pick up the address and use it without any fuss. And you only need to use one register to point to an item, and you've got 15 to choose from so you can point to a bunch of different data items at the same time without loading and storing pointers all the time. It's not really fair to call the 370 a "segmented" architecture. It's a linear architecture, but there is no absolute addressing mode (except for the first 4K). Where this gets annoying is for branching... -- Doug Pardee -- Terak Corp. -- !{ihnp4,seismo,decvax}!noao!terak!doug ^^^^^--- soon to be CalComp