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Reset and NMI Switch for TurboTrans

Project: Reset and NMI switch for the TurboTrans.
Target : TurboTrans
Time   : 15 min.
Cost   : ~2 US$
Use    : - easily switch RAM banks and read disks into RAM.
         - reset hung up floppy without need to switch floppy on/off.


Push-button switch between ... and pull-up resistor to pin 5 (all pins refer to the soldering pads on the TT board in the 1541.


Reading a disk into the TT's RAM and swapping RAM banks can be accomplished by issuing the appropriate command to the floppy. However, both functions can be executed by simply pressing a button. Alas, Roßmöller has saved the pull-up resistor for the NMI switch, so you have to add one yourself.



  1. Remove all cables, then open case.
  2. Solder the wires to the two switches.
  3. Solder one switch between pin 5 of the soldering pads depicted below and the pin above (GND), this will be the NMI switch.
     o-o-o-o-o-o-o-o  <- ground
     o o o o o o o o
     1 2 3 4 5 6 7 8
  4. Solder the other switch between pin 6 and the pin above (GND), this will be the reset switch.
  5. Below the 16 solder pads on the top you can see a large ground pad with a hole in it and three solder pads to the right. Solder the resistor between the top of the three pads (+5V) and pin 5 of the upper 16 pads (pin 5 means the LOWER pin of the two, otherwise you would shortcut +5V and ground - ouch!).
  6. Test both switches. Pressing the NMI switch once will switch the RAM banks. When you press it once, wait for the floppy LED to light up, and then quickly press it again (with the LED still on), the TT will read the disk into the current RAM bank.
  7. If it seems to work, close the case again.

Possible failures

Updated: December 5th, 1997
Created: December 5th, 1997
Status : Verified on December 5th, 1997

Site copyright © 1997 by Marc-Jano Knopp
This document is part of MJK's Commodore 64 & LCD Page
Brought back to life by Peter Schepers, Dec 10, 2005 because I really liked this site!