Serial, 115Kbps, 2.2, 2.4

Serial, 115Kbps, 2.2, 2.4

[Trever L. Adams]

I am trying to find out if I am the only one who has pppd drop packets 
as bogus when the port is set at 115Kbps.  I only get it at that speed. 
  It causes stall outs etc.

There may be a possibility this is machine specific, because if it is 
meant to forward the packet to the internal net and I slow the machine 
down (external cache off) it works fine, turn the cache back on and it 
is a problem.

So, anyway, this is an information seeking trip.

Trever

Re: Serial, 115Kbps, 2.2, 2.4

[Jeff Chua]

On Sun, 1 Apr 2001, Trever L. Adams wrote:

> I am trying to find out if I am the only one who has pppd drop packets
> as bogus when the port is set at 115Kbps.  I only get it at that speed.
>   It causes stall outs etc.
>
works fine for me.

Jeff

Re: Serial, 115Kbps, 2.2, 2.4

[Manfred H. Winter]

Hi Trever!

On Sun, 01 Apr 2001, Trever L. Adams wrote:

> I am trying to find out if I am the only one who has pppd drop packets 
> as bogus when the port is set at 115Kbps.  I only get it at that speed. 
>   It causes stall outs etc.
>

I also have some problems with pppd. At my machine it says sometimes:

Couldn't set tty to PPP discipline: Invalid argument

I'm also using the serial port at 115Kps with a USR Sportster Voice
33.6.

Manfred
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Re: Serial, 115Kbps, 2.2, 2.4

[Trever L. Adams]

Mark Hahn wrote:

>> There may be a possibility this is machine specific, because if it is 
>> meant to forward the packet to the internal net and I slow the machine 
>> down (external cache off) it works fine, turn the cache back on and it 
>> is a problem.
> 
> 
> where's the serial port?  (isa, pci?)  could there be a problem
> with something being overclocked (like >8 MHz ISA, etc)?
> also, is the port's fifo detected and used?


As far as I know the system is not overclocked (standard Digital 
Venturis 6200 GL PPro 200 Mhz machine).  It is an ISA modem.  All info I 
have on the port is as follows:

Serial driver version 5.05 (2000-12-13) with MANY_PORTS SHARE_IRQ 
SERIAL_PCI ISAPNP enabled
ttyS00 at 0x03f8 (irq = 4) is a 16550A

cat /proc/ioports
03f8-03ff : serial(auto)

It is a USR 56K Voice/Fax/Modem.  I am unable to find the exact model. 
It was definitely pre v.90 though I believe it has been updated 
(Firmware) to that.  I have another, though I don't remember similar 
problems even though it was at the same baudrate (different machine though).

Trever Adams

Re: Serial, 115Kbps, 2.2, 2.4

[Tom Sightler]

Actually, I do have a similar problem that I've been unable to track down
100%.  Under 2.4.x when I run the modem on my Xircom Cardbus 10/100
Ethernet/56K Modem combo card (installed in a Dell 5000e with 650Mhz Pentium
III) I get a fair number of dropped packets at 115Kbps, enough to cause
problems and a significant speed decrease.  Simply dropping the serial port
rate to 56K seems to solve the problem.  I'm actually suspicious that the
hardware handshaking isn't working quite right, but I haven't take the time
to look at it.

I never noticed the problem under 2.2.x, but the last kernel I ran from that
era was the 2.2.16 kernel included with Redhat 7.  I've really not looked at
it very hard, backing the speed down to 56K was a good enough solution for
me for now, the Xircom has such a troublesome history that I just blamed it
on that but your report makes me more curious.

Later,
Tom

Re: Serial, 115Kbps, 2.2, 2.4

[Paul Jakma]

On Sun, 1 Apr 2001, Tom Sightler wrote:

> III) I get a fair number of dropped packets at 115Kbps, enough to cause
> problems and a significant speed decrease.  Simply dropping the serial port
> rate to 56K seems to solve the problem.

does the system have IDE disks? (DEC Venturis GL.. should be)

Try hdparm -u on all your IDE disks... should improve things.

> Later,
> Tom

regards,
-- 
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