ROM programming
The ATW800/2 for the Mega ST bus features two flash ROMs that provide space for four 256 KB TOS images.
The DIP switch at the back of the card can select these ROMs. Looking at the DIP switch from the back of the card, the switches read 1 and 2 from left to right:
| Slot # | Sw1 | Sw2 | Default ROM |
|---|---|---|---|
| 1 | Down | Down | TOS 2.06 |
| 2 | Up | Down | Latest EMU TOS |
| 3 | Down | Up | Previous EMU TOS version |
| 4 | Up | Up | TOS 1.04 |
Disabling the ROMs
Depending on your board revision there are diffrent ways to disable the onboard TOS ROM.
Revision 1.1b and later
Owners of the most recent card revisions can simply pull the jumper marked with “ROM enable” on the card.
Revision 1.1a
Owners of ATW800/2 with a revision of 1.1a can also use this red jumper but also need to do a tiny little bit of soldering. Due to a design mistake, the left pin of the jumper needs a connection to a 5V source. This is for example available at the 3rd pin from right of TRAM socket “SLOT 2” using a jumper wire on the backside of the card.
Revisions previous to 1.1a
Owners of the early card revisions need to physically remove the ROM chips from their sockets.
You can do this by using either a dedicated PLCC pulling tool (shown below on the left) or a thin but sturdy tool and carefully sticking it into the notches in the corners of the socket one side at a time. Gently remove the ROM chip by lifting it up a little on each side. After a couple of lifts, it will pop out.
The PLCC package was intentionally chosen because this allows removing the ROM chips and external programming by using an EPROM burner/programmer/"blower".
That said, the PLCC sockets are not made lots of insertions and removals and will wear out pretty quickly.
So try to keep the number of in's and out's as low as possible!