Strange autosense thing

Hi

My home network of 5 pc's, has 3 systems with a 3c905 and two with a
cheap builtin card. Center of it all is a 3com 100Mb fixed hub. Lately I
noticed that my network was slow and when using qcheck it turned out it
was reeeeeeeeeeeeeaaaaaaaaaaaly slow.... about 200kb/sec !!!

I updated drivers, check the hub, tried severall things, nothing helped.
Then someone told me to play with autosensing. I did remember setting
all cards to fixed 100mb full duplex. So I changed one card to
autosensing and wow !!! 67Mb/sec !!!

After that I changed all cards to autosense and everything is now
running very fast.

Can someone explain or redirect me to an url, on how autosensing works?

Gabrie