From: muta...@gmail.com   
      
   On Friday, June 18, 2021 at 10:14:22 AM UTC+10, anti...@math.uni.wroc.pl wrote:   
      
   > Translation between 8-bit code pages can be done via   
   > table lookup. That costs 512 bytes (for two way   
   > translation) and single indexed memory access per   
   > character. This is not much burden, either for   
   > software or for hardware.   
      
   I would like simple comms programs to work out of   
   the box so long as both ends are EBCDIC or both   
   ends are ASCII. I expect "ATDT" to work.   
      
   > However, you need to   
   > know which code page to use and when.   
      
   Most people don't support EBCDIC at all. I support one   
   single EBCDIC codepage. Other EBCDIC codepages are   
   supported if they survive the 819 to 1047 transition. I   
   don't know how many that is. But all other EBCDIC users   
   can find their own solutions.   
      
   > Sofware   
   > simply is better place to put translation because   
   > it anyway needs to know about state of connection,   
   > so switching translation tables comes naturally.   
      
   Not sure what you mean by "state of connection".   
      
   > But I will stop arguing here. Apparently you   
   > love solutions that other folks find awkward.   
   > Since you are doing this, ulitmately your   
   > opinion is most important here.   
      
   Very diplomatic. :-)   
      
   > connector. He also said that transmissin was   
   > via interrupts and that "IBM does not like   
   > interrupts". I take this to mean that each   
   > character triggered a separate interrupt.   
   > My guess is that the guy connected "external   
   > interrupt" line (which IIUC is standard thing   
   > for IBM processors) to parallel-port style   
   > connector so that modem could interrupt the   
   > mainframe. Concerning "IBM does not like   
   > interrupts": transmiting one character per   
   > interrupt was horribly inefficient by IBM   
   > standards. Since this was single line, there   
   > was no problem. But the machine had probably   
   > about 80 terminals connected using standard   
   > IBM interfaces. Running 80 terminals in   
   > async mode probably would not work (I mean   
   > running in hacky way without something   
   > like 3705).   
      
   I would hope that after 30 years (or whenever you were   
   doing this) of technology improvement that mainframes   
   can now cope with 80 terminals where previously they   
   could only do 1. I wonder what percentage of a modern   
   z/Arch CPU would be consumed coping with 80 monkeys   
   banging away on keyboards as fast as they can, with   
   each keystroke causing an interrupt.   
      
   BFN. Paul.   
      
   --- SoupGate-Win32 v1.05   
    * Origin: you cannot sedate... all the things you hate (1:229/2)