abl@cernvax.UUCP (abl) (04/19/88)
I have an application running on an IBM PC/AT running IBM Xenix 2.00 that uses high speed serial transfer (9600 baud) to communicate with other machines. The protocol used is similar to Kermit in that all data is sent in packets and retries are performed if a transfer fails. The problem is that Xenix does not get a lot of the characters sent to it. Around 1% are lost when the machine is unloaded and much more if there is another process with a high level of interrupt driven input/output (e.g. other tty activity or network activity). I would imagine that this is an old and solved problem for most of you so any advice would be appreciated. What prompted this request now is that we have recently received a copy of SCO Xenix 2.2.1 and the documentation includes some comments about the 8250a serial chip used by most serial ports used on PC/ATs. It claims that there are problems with the interrupt handling on this chip and that they where fixed on the 8250b. Our IBM and AST advantage serial ports use the NS16450N chip - is this the same as the 8250a and has it the same problems? Other questions while I am here: 1) Do serial cards like the Digiboard COM /4, /8, /4i or /8i solve all known serial problems and if so where can I get one in Europe? 2) Does SCO Xenix solve problems associated with the 'no more processes' messages that IBM Xenix 2.00 sometimes gives when two or more large programs are running? We think that these problems are due to bugs in IBM Xenix 2.00 memory management - it is not a problem with the number of processes. We also have problems with 'no more processes' when using programs which communicate via shared memory. Thanks in advance, Alastair Bland, SPS, CERN, Switzerland. abl@cernvax.cern or abl@lepxs.cern