921kbps ppp line - problems

[Wojciech Puchar]

here is my config

default:
  set log Phase Chat LCP IPCP CCP tun command
  disable dns

stalka:
  set device /dev/cuad4
  set speed 921600
  add default HISADDR
  disable deflate pred1 deflate24



FreeBSD 6.0 on this side, puc/sio compatible interface (TITAN-800H PCI, 
8 port interface), NetBSD-current on other side. connection generally 
works but

Nov 19 21:42:31 chylonia ppp[1144]: tun0: Phase: deflink: HDLC errors -> 
FCS: 50, ADDR: 0, COMD: 0, PROTO: 0

and actually there are detectable packet loss and big slowdown on 
transfers.

there is NO silo overflow errors in kernel!

what i missed?

to be clear - i have NetBSD here before and connection worked fine, so 
line/modem is OK.