> 
> Hi,
> 
> Ever since I began using the ALPHA source, I have been getting errors like
> this:
> 
> Jun 23 04:50:03 gelatin /netbsd: zstty0: fifo overrun
> 
> I'm using ppp, connected to my modem at 38400.  I'm using a Performa 550.  
> Anyone know why I'm getting this error?

Yep. There's a bug somewhere in the scsi driver which goes away when splimp()
gets set tp spl4(), not spl2(). In other words, when splimp (sets the
processor's interrupt level so that nothing which might allocate memory
gets called) blocks the serial port interrupts in addition to blocking
via2 interrupts, the bug stops biting.

No one really knows where it is. My thought (unsubstantiated, of course)
is that it's a weird timing problem. If a character arrives in the
middle of some scsi write, certain targets get freaked out by the pause
from the mac servicing the interrupt. Raising splimp's blocking effects
will make this timing work fine. Unfortunately a lot of code likes
to live at splimp, so we loose lots of tty characters.

splimp was recently lowered back to spl2 in -current sources (past few
days), so all will soon be well.

Take care,

Bill