I get "RAM 00100000" on my screen when I hold both Apple keys down during boot. I can remove all cards and get the same thing. I have replaced the 3rd of 8 RAM chips, after desoldering suspect RAM and soldered in a socket before putting new RAM in. The 4th and 5th chips are also socketed and I tried swapping those as well. I can enter and run a BASIC program, but booting from floppy doesn't work. Help!