MODIFY YOUR FAST LOAD FOR THE 128 
 By: Bruce Jaeger 

 Copyright 1986 Twin Cities 128 
 P.O. BOX 4625, Saint Paul MN 55104 
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 article: 

 We don't like to talk much about the C-128's Commodore 64 mode in Twin Cities 128. Occasionally, though, we realize that there will always be more C-64's than C-128's (because every C-128 sold also adds to the C-64's total!) and that the software publishers will almost always opt for the most common machine. Hence, we often have to lobotomize our C-128 down to 64K, and take the 1571 Indy Car-speed disk drive, install a lawn-mower engine with bad rings and a shot magneto, and call it a 1541. 

 Epyx's Fast Load cartridge is a pretty effective product for getting those Commodore 64 games and utilities to load faster. While not all programs can be loaded with it (due to "protection" schemes that further confuse the poor 1541), the Fast Load cartridge will load most programs much faster than the standard DOS, with the added bonus of making the famous "DOS Wedge" disk command shorthand available to the 64 user, as well as several other utilities. 

 On the minus side, to use the Fast Load cartridge with the C-128 means that you have to install the cartridge when you go to C-64 mode, then remove it to go back to 128 mode. If you're a software developer (or just an avid C-128 user) this is going to mean a lot of wear and tear on the cartridge port, as well as frustrating waits for power-up if you turn off the computer between cartridge changes (as you're supposed to), or risk frying a chip or two by yanking the cartridge in and out under power (as anyone with a normal human's patience tends to start doing eventually!) Fortunately, there's an easy way out, and you don't have to be overly handy with a soldering iron. By putting a switch in the EXROM line between the Fast Load circuitry and the circuit board pads, the C-128 can be made to ignore the presence of the cartridge. Open the switch, and the C-128 will come up in 128 mode, because the cartridge can't assert the EXROM line to the cartridge port. Close the switch, and the C-128 will come up as a C-64 (after power-up, or simply pressing the reset button), with the Fast Load utilities enabled. And as a little extra bonus, the Fast Load cartridge gets you to C-64 mode a lot faster than "GO 64" or the reset-with- Commodore-key methods! 

 Here are the simple step-by-step instructions for adding the switch to your Fast Load cartridge. Not that the photos may look slightly different from your own Fast Load; that's because I made the modification to mine, then unsoldered everything (once I knew it worked!) to take the photographs.  

 STEP 1: OPENING THE CARTRIDGE: 

 Slit the paper cover where it wraps around the back of the cartridge. Pick away the paper from the screw holding the two cartridge halves together (Figure 1). Unscrew the screw, using a small Phillips-head screwdriver, and carefully pull the two cartridge halves apart.  

 STEP 2: DRILL THE SWITCH MOUNTING HOLE: 

 There's plenty of room in the top portion of the cartridge (near the Epyx name) for a small SPST toggle switch. (SPST means "Single Pole, Single Throw." It's the cheapest, least confusing type. Get a small one at Radio Shack.) Using a drill appropriate for mounting the switch you have on hand (mine was 1/4"), drill a hole in the top half of the cartridge where you want the switch to go. (See Figure 2.) If you like, you can install the switch now in the cartridge top; it will make it easier to solder to later.  

STEP 3: CUT THE EXROM TRACE: 

 The trace (that's electronics talk for those little copper paths on the circuit board) that we want to cut is the EXROM line. No, it's not labelled on the circuit board! Looking down at the board with the PC pads (that connect to the 128's cartridge port) towards us, count nine pads from the left; that's the EXROM line. (Also see Figure 3.) Using an X-Acto knife or similar tool (CAREFUL!), cut away at the trace until you are just through the copper, and it is no longer a good connection from the pad to the 7407 chip. Don't make your cut too near the chip, or too near the edge pad, as we'll need room to solder wires leading to our switch. 

 STEP 4: SCRAPE INSULATION: 

 You've probably noticed that the copper trace was coated with some translucent green varnish-like stuff. We can't solder to that, so use the X-Acto to carefully scrape off the varnish on either side of the cut we made. 

 STEP 5: SOLDERING WIRES: 

 This is probably the trickiest step, because the tiny traces aren't really designed to be soldered directly to, and can be pulled away from the board if we aren't careful, or use too much heat. If you're at all unsure about soldering in close quarters, get someone with more experience to help you. 

 First, find two 3" long pieces of thin, flexible wire. (Remember, it's got to be tucked up inside the cartridge with your switch, and the whole mess screwed back together!) Remove about 1/8" of the insulation from each end of each wire. "Tin" the ends by heating the wire with your soldering iron, and apply ROSIN-CORE solder until the ends of the wires are shiny. 

 Now, carefully tin the exposed copper of the scraped traces, being extra careful not to flow solder into the gap you laboriously cut! DO NOT do this soldering on the circuit board with a big, clumsy soldering gun -- they provide too much heat, which could buckle the board or make the trace pull away. (And if you even considered using a torch to do your soldering, please sell your computer and go get a job as a tornado-rod salesman.) 

 Tinning your wires and traces will make soldering them together easy. Lay the exposed end of a wire on top of a tinned trace, press the iron on top of them and Presto!, they're soldered together. Repeat for the other trace. Figure 4 shows my wires soldered in place. They're not so neat, because I reheated my joints several times in installing and removing the wires for the photos. Do yours once!  

 STEP 6: SOLDER THE WIRES TO THE SWITCH: 

 This is easy, unless you made your wires a bit too short! Just "tin" the terminals on your switch, then solder the other ends of the wires to the terminals. (See Figure 5.) It's not overly important which wire goes where, as long as the connections are good. 

 If you haven't already mounted the switch to the top half of the cartridge box, do so now. 

 STEP 7: PUTTING IT ALL TOGETHER: 

 CAREFULLY put the two cartridge halves back together, taking extra care that your wires don't stick out the sides. Be especially careful that you don't inadvertently pull the wires off their soldered connection to the traces--that's a very fragile connection! When everything fits, screw in the locking screw (Figure 1) and tighten. Now for testing! 

 STEP 8: TESTING, LABELLING THE SWITCH 

 Turn OFF your computer. OFF! Now plug in the cartridge. If you are using a 1902 monitor, turn it to 40-column mode (so we can see the C-64 mode screen if it comes up). 

 Turn on the computer. It will come up in either 128 or 64 mode. Flip the switch in the opposite direction, and press the reset button on the side of the C-128. The computer should now come up in the opposite mode. Label your switch appropriately. 

 TROUBLESHOOTING: 

 If, for some reason, the computer keeps coming up in C-64 mode, you've got a "short" in the new wiring somewhere. Make sure solder hasn't bridged the gap you cut in the trace, and that the wires are distinct and separate all the way to the switch terminals and back. (Also make sure, of course, that it was the EXROM trace you cut and installed wires on! Refer to Figure 3 to make sure)! 

 If, on the other hand, the computer keeps coming up in C-128 mode, no matter where you set the switch, it means that the switch is not re-connecting the cut trace. Check for bad solder joints, a broken wire (they can do that sometimes, without you suspecting it) or for a bum switch if you pulled it out of your scrap box.