And we should note, for those who might try to use this information, that A0 and A1 are not connected to the address pins on the ROM chips on the module. A2 of the ROM SIMM connects to A0 on the ROM (or Flash) chips. However, this may vary a bit on the SE/30 and one earlier machine. I need to go check the book again darn it. The concept is that the ROM SIMM is 4 bytes wide and A0 and A1 would be for addressing individual bytes of the word. In other words the ROM SIMM address pins are numbered for byte-wise addressing, while in practice the ROM SIMM is wired for word addressing (four bytes per address).