You are remembering correctly Byrd. The 128K & 512K were essentially identical except for RAM. The 512Ke was a 512K with a Plus ROM (the Plus being essentially being identical to a 128K except for more RAM and built-in SCSI hardware). A few folks on here have even put a Plus ROM in a 128K to get SCSI capabilities, as well as native support for Apple's 800K drives and HD20. The ROM compatibility breaks with the SE.