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Kickstart Switcher
Rämixx500 has an integrated Kickstart Switcher. If you want to use it, start by locating jumpers J91-93, which sit right above the ROM socket and are shaped like a Tetris piece. If you haven't touched them yet, each of them will have a horizontal trace connecting the two middle pins (this position is marked as DIR on the silkscren, standing for DIRect Connection). You will need to cut all the three of these traces, the suggested place for the cut is marked with a vertical white line. Use a multimeter in Continuity Check Mode to make sure the connection is really interrupted and solder pin headers to all pins. Now you can place jumper caps vertically to force the ROM to see the A18-A20 lines as permanently high or low, which will allow you to select one among different slots as follows.
Kickstart versions older than 2.0 are all 256k in size. You can use the A18/19/20 jumpers and switch among up to 8 slots with a 27C160 EPROM (2 MB):
| Slot # | A20 | A19 | A18 | Address Range |
|---|---|---|---|---|
| 1 | LO | LO | LO | $000000 - $03FFFF |
| 2 | LO | LO | HI | $040000 - $07FFFF |
| 3 | LO | HI | LO | $080000 - $0BFFFF |
| 4 | LO | HI | HI | $0C0000 - $0FFFFF |
| 5 | HI | LO | LO | $100000 - $13FFFF |
| 6 | HI | LO | HI | $140000 - $17FFFF |
| 7 | HI | HI | LO | $180000 - $1BFFFF |
| 8 | HI | HI | HI | $1C0000 - $1FFFFF |
If using a 27C800 EPROM (1 MB) you will be limited to 4 slots, as you will have to keep A20 HI.
Kickstart versions from 2.0 onwards are all 512k in size. This means that the A18 jumper will have to stay in the horizontal DIR position, but you can use the A19/20 jumpers to switch among up to 4 slots with a 27C160 EPROM:
| Slot # | A20 | A19 | Address Range |
|---|---|---|---|
| 1 | LO | LO | $000000 - $07FFFF |
| 2 | LO | HI | $080000 - $0FFFFF |
| 3 | HI | LO | $100000 - $17FFFF |
| 4 | HI | HI | $180000 - $1FFFFF |
If using a 27C800 EPROM you will be limited to 2 slots, as you will have to keep A20 HI.
You can mix and match 256k and 512k slots freely, as long as you understand what you are doing and set the jumpers correctly. The Address Ranges in the tables above should help you with this.
You can also wire SPDT switches to the J91-93 jumpers and leave them hanging in your trapdoor if you want to be able to change your Kickstart image without opening your Amiga (Warning: Drilling holes is frowned upon!). Note though that this is a pretty basic method of switching ROMS. If you want a more advanced switcher, place all your jumpers in the DIR position and have a look at OpenKickstartSwitcher.