8-port serial async cards??

[Paul De Bra]

In article <2870 at ddsw1.MCS.COM> karl at ddsw1.UUCP (Karl Denninger) writes:
}>...
}>I haven't timed it - but Anvil says throughput to the board is in excess of
}>160kbs - it can sustain 9600 to 16 ports at a time.  It also goes up to 38k.
}>...
}ARGH!
}
}The Anvil board may be fine for 16 terminals, but I wouldn't think of using
}it with even TWO 19200 baud modems.
}
}Why?  Because they haven't done the work required to get the board to handle
}input at that speed.
}
}Yes, this is only about 20kbs -- TERRIBLE performance on input.
}
}Admittedly, output is much better -- as long as there's no input going on!
}I don't know if I buy 160kbs though....
}
}When our Telebit comes online, my "19200" baud serial terminals' display
}rate goes down to under 9600 bps -- because the board is overloaded and
}giving priority to the input (thank god they did get this right).

You realize you are being very demanding (even for a board with an
8Mz 80186). We used to have an old Altos, with controllers for 8 terminals.
We used 1 port for 4800 baud uucp-input, and the others for 9600 baud
terminals. Any uucp traffic (input) on the one port would visibly slow
down output on the other terminals (even when using only one) to 1200 baud.
Those boards used a 4Mhz Z80 I believe.

So I doubt whether there is much they can do to inprove the  Anvil board
by much. If we rate the processor at about 0.5 MIPS, and we assume
19200 baud input and output on all 16 lines, that is over 60000 chars/sec
together, that leaves less than 10 instructions to handle a single char.
No way this can be done. What they claim (160kbs) corresponds to 16 lines
at 9600 baud in only one direction, but even then you have only about
40 instructions to handle a character. This could be hairy already.

Paul.
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