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    SubjectRe: Dreadful xfer rates and TCPv4 bad checksum in 2.1.1xx with PPP
    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.


    Brian Gerst

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