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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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