The motherboard RAM for PB 280 is 4 MB, maximum RAM is 40 MB, number of sockets is 1 - unique socket, minimum speed is 70 ns The motherboard RAM for PB 2300c is 8 MB, maximum RAM is 56 MB, number of sockets is 1 - unique socket, minimum speed is 70 ns ---> Thanks on both. Based on memory specs both duos can use the same memory chips. Operating systems that is most effective for PB280 is 7.6.1 while the PB2300c is Mac OS 8.6 ---> Yeh I see that 9.1 can run on the Duo 2300c much like the limit of a lot of 603 type computers that were made. (Like my A/V 6600). 8.6 sounds about right. I guess you can run Yahoo messenger and few other things. To me the 2300c feels about the same running speed as the 280c, it is just that newer software more or less starts at system 8.5 So anyone ever make a processor upgrade for these things?