Have I tried too hard to squeeze usability out of an old computer?

I have a Pentium-166 that has been a faithful router & firewall (FreeBSD
5.3 and pf) for a couple years now. It has no trouble with the 3 to 4
Mbps I get from my broadband connection, at least not with ethernet.

I wanted wireless, so I could use my laptop around the house. I
dutifully read the section in the manual about setting up FreeBSD as an
access point. I'm using a Netgear MA311 802.11b card (Prism 2.5
chipset). And it does work, except it's very slow. Now I know that I
can only expect about 50% of the rated speed with wireless, but I
figured even if I got only 4Mbps, I'd be fine. But I get less than
1Mbps. I've updated the firmware, added a signal booster and hi-gain
antenna, and I have "excellent" signal strength throughout my house.

So my question is, is there more overhead with wireless than with
ethernet? TOP doesn't seem to show that I'm taxing it too hard, idle
never goes below about 70% with polling enabled (Hz=1000), and never
below about 80% with polling disabled. Am I expecting too much out of
an old Pentium-166?

Thanks for your help.

Christopher