Re: lost serial characters

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Addenda:
I don't believe I'm using a frame buffer.  The command fbset returns 'error: /dev/fb0: no such device'.  I seem to confirm this with 'cp /dev/db0 testfile'.
 
Kurt

Mark Vojkovich <mvojkovi@xxxxxxxxxxx> wrote:
On Tue, 2 Nov 2004, kurt emmerich wrote:

> I hope this is the right place to ask - if not I apologize- would someone please point me in the right direction?
>
> I'm running Fedora 1 on a 400MHz Pentium 2. Runs great, no problem, except when using the KDE or GNOME desktop. When receiving serial data ( /dev/ttyS0) 115200,8,n,1, I'm losing characters. Looks to me like the serial receive interrupt is getting 'stalled'. This occurs at bauds as low as 19200 ( I dont recall if I tried lower than that) and gets must worse as I drag windows aroung the screen with the mouse.
> However, when I open a text console ( ctrl-alt-f1) and run minicom from there, I can successfully receive well over 150M of data with zero errors even at 115K baud. Hardware handshaking is enabled and asserted.
>
> Might I ask for feedback on this? Has anyone else seen this? Any opinions on why this is occurring??
>
> Thanks,
> Regards,
> Todd

Which graphics card and driver? Which AGP chipset (ie. LX, BX, etc...)?
Your XFree86 driver isn't using a framebuffer device is it?
Is the serial port sharing an interrupt with something else?

I suspect a shared interrupt or a "PCI retry" problem. PCI retries
are usually caused by the graphics driver and are particularly a problem
on Intel LX chipsets. Historically, this has caused problems with
sound cards, but I suppose it could effect serial as well.

Mark.
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