SLOAN%MIT-OZ@MIT-MC.ARPA (11/04/83)
Well, I have the first edition (August 1981) of the Tech. Ref. Manual, so I had a bit of a problem following your page references, but I found similar information on pages 3-21 and 3-22. Here follows my opinion: 1) A typical implementor's defense of IBM's use of interupts in the 0-1f range might be: "WE used them, but you aren't supposed to. If you do, you do so at your own risk. YOU are supposed to use DOS. If WE want to use 80188's, then we will change our code - which you will buy, because the code you already have (from us) is only licensed for use on the PC you bought it for, and no other machine! Just buy the new, improved DOS version 4.2 (oops, sorry!) and all will be well." 2) The rest of the world might say: "But, you did such a bad job of implementing such things as RS232 support, and such a good job of documenting it, that we replaced your code with ours, and embedded it in products, which we magnanimously sold for unlimited use on any processor. Looks like we have a serious customer support problem!" And, they are both right: folks who read ONLY the IBM Tech. Ref. Manual and bravely used the BIOS calls, and replaced the thinly documented RS232 interrupt slot have some right to complain, but not all that much. The whole point of DOS is to provide standard, rarely changing interfaces to an abstract machine. If you want to hack the hardware, or the BIOS - you were happy to see the source listings, but should have been a bit more careful. So it goes... Ken Sloan