Congrats on getting the Duo on the net. That is a rather clever solution.
Perhaps it isn't as fast as ethernet, but it could still be quite fast.
Back when I first got DSL (and before hardware routers were affordable), I ran IPNetRouter on my Quadra 840av to share the DSL between several Macs and a PC. Most of the computers were on ethernet, but my Powerbook Duo 280c was on LocalTalk. The Quadra must have been able to pump up the serial port speed past what was normal for the Duo, because the Duo could download files via FTP at around 80KB/sec. That is equal to 640kbps, which is much faster than the typical 130kbps it should have been getting, and pretty close to the 768kbps DSL I had.
For comparison, the Centris 650 Macs that I had in my computer lab in college would get between 80-100KB/sec download rates over ethernet. Any way you look at it, it will be leaps and bounds better than dial-up.
I am not sure what your USB-to-Serial adapter is capable of, but the one I have here at work handles rates up to 230kbps.
From the way I understand it, you are using direct serial communication between the Powerbook and iMac. That is where the 1-to-1 ratio lies. If it was doing LocalTalk (MacIP for TCP/IP networking), then you could have approx. 250 computers daisychained to your iMac. AFAIK, serial communications are limited to 2 devices though.
Perhaps it isn't as fast as ethernet, but it could still be quite fast.
Back when I first got DSL (and before hardware routers were affordable), I ran IPNetRouter on my Quadra 840av to share the DSL between several Macs and a PC. Most of the computers were on ethernet, but my Powerbook Duo 280c was on LocalTalk. The Quadra must have been able to pump up the serial port speed past what was normal for the Duo, because the Duo could download files via FTP at around 80KB/sec. That is equal to 640kbps, which is much faster than the typical 130kbps it should have been getting, and pretty close to the 768kbps DSL I had.
For comparison, the Centris 650 Macs that I had in my computer lab in college would get between 80-100KB/sec download rates over ethernet. Any way you look at it, it will be leaps and bounds better than dial-up.
I am not sure what your USB-to-Serial adapter is capable of, but the one I have here at work handles rates up to 230kbps.
From the way I understand it, you are using direct serial communication between the Powerbook and iMac. That is where the 1-to-1 ratio lies. If it was doing LocalTalk (MacIP for TCP/IP networking), then you could have approx. 250 computers daisychained to your iMac. AFAIK, serial communications are limited to 2 devices though.