Poor Latency using Digiboard 16em

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1 total messages Started by bigdaddy_paul Thu, 21 Oct 1999 00:00

#5998

Author: bigdaddy_paul
Date: Thu, 21 Oct 1999 00:00

22 lines
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I am attempting to communicate with a number of external devices via
115200 bps async serial connections brought in to an AlphaServer 800 by
a Digiboard 16em. The Alpha is running DEC Unix 4.0f. The external
devices are polled in a half-duplex manner. Each message (inbound and
outbound) is relatively short (In the range of 10 to 250 bytes). The
external devices respond to the poll requests with latencies in the
range of 2 to 5 milliseconds. However, I am observing latencies in the
range of 15 to 30 milliseconds when using getclock to fetch timestamps
at the start and end of the exchange. I have set the poll parameter for
the Digiboard using Digi's ditty utility to its shortest value of 2000
microseconds.

I would be most grateful for any useful suggestions including other
hardware that could be used instead of the Digiboard that would perform
better (A minimum of 8 ports must be supported with 16 being the
preferable value).

Paul Wilson


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