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    SubjectRe: Dreadful xfer rates and TCPv4 bad checksum in 2.1.1xx with PPP
    Brian Gerst wrote:
    >
    >David G Hamblen wrote:
    >>
    >> Responding to my own post, I've got a little more info. I borrowed a
    >> Gateway Telepath xjack pcmcia 33.6 fax/modem, and it works fine at
    >>33.6K.
    >> Conclusion: something about my serial port (16450) and the serial
    >>driver
    >> is garbling data. The internal modem on COM2 and the Hayes modem on
    >>COM1
    > both give lots of checksum errors and slow transfers at 14.4, while the
    >> pcmcia modem works well.
    >
    >If it's a 16450, that's your problem. you need a 16550(a) to reliably
    >handle speeds above 9600 bps. The '450 doesn't have a FIFO, so an
    >interrupt is generated for _every_ byte sent/received. This leads to
    >dropped characters, hence the checksum errors.


    Yes, but the 16450 works on Win95, linux 2.0.33, and linux 2.1.xxx
    thru the mid 80's.


    Dave



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