I ran across a mystery this weekend while working on a couple of A3000s that I am repairing, and I was hoping that someone here could shed some light.
The A3000 has a 32-bit bus to the ROMs, of which there are 2, and they are 16-bits each. I verified that data line D0 goes to the ROM socket which is labelled ROM0, so presumably we have D0-D15 going to ROM0 and D16-D31 going to ROM1. So far, so good.
However, in order for the computer to work properly, you must install the chip which labelled as ROM1 (390630-03 for v2.04) into the socket labelled ROM0, and vice versa. Now that's just messed up. Also, by reading the data off the ROM, it can be seen that the high 16 bits are on the chip labelled ROM0 (which goes into the socket labelled ROM1).
It seems to me that the chips are just mis-labelled. Is this something to do with big-endianness? Can anyone explain? Thanks!