Mandrake Single Network Firewall problems

I installed the SNF on a P133 with 40MB ram and it is just not keeping up
with my connection. I thought given the fact that SNF does not run X this
would be ok as I am on a cable modem. I can boost the ram to 64 and see if it
will keep up then. I have no logging activated on a 24/7 basis because the HD
is only 350MB and likely a 3300rpm drive. I noticed after about two days
of running SNF my connection really slowed down. I know some of this may be
excess traffic being generated by Code Red but I disconnected the firewall
and tried the test at DSLreports.com and got nearly normal results.

Firewall on at dslreports: 60-120k down
Firewall off at dslreports:1800-2000k down (coble modem -->Wkst. NIC direct)
Tests prior to code red: 2400-2800k down

I use dslreports and others and have become aware of what to expect from
each site. The above results are definitely not normal.
Is the cable modem just too much for the machine that is trying to run the
firewall?

TIA,
John W