Messages in this thread | | | Date | Fri, 06 Nov 1998 17:50:17 -0500 | From | Brian Gerst <> | Subject | Re: Dreadful xfer rates and TCPv4 bad checksum in 2.1.1xx with PPP |
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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.
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Brian Gerst
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