My Amd586-133 suffers from the slow-PPP problems when it is run
with a 33Mhz clock in 4X mode, but hasn't dropped a packet since
I changed it to a 50Mhz clock and 3X mode and both L1 and L2 caches
in write-back mode.
Since changing the clocking, I haven't had any problems with any
version since 1.3.81 thru 1.3.85. My old PPP problems seemed to
be missing bytes, as frames where being dropped due to FCS errors.
I sure that you know, the PPP driver does not support throttling
of the sender (see: ppp_tty_room). The driver assumes that it will
always be fast enough to accept anything sent to it. NCFTP has reported
>10Kb/sec thru-put receiving uncompressed source files over a 24K baud
connection. If I ever get connected at 28.8K, this could be 20%
faster. The receive buffer is allocated as 1584 bytes, which could
be filled in 0.15 sec. at 10Kb/sec. If there is no room in the receive
buffer, the driver just drops them into the bit-bucket!
I'm using ppp-2.2.0e, gcc-2.7.2, libc-5.2.18.