Commodore 64

VIC-II² C64 PAL/NTSC SwitchEr

Abstract:

The VIC-II² C64 PAL/NTSC card offers an easily-switchable NTSC or PAL solution for Commodore 64 users.

Background

In late Summer of 2018, Christian Simpson aka Perifractic and I began collaboration on a project that would become the VIC-II² Card (pronounced VIC-TWO-SQUARED). Our shared love of Commodore 64 and retro technology made it an easy partnering. Christian had already performed a conversion of an NTSC version of the C64 to PAL as part of his Retro Recipes YouTube channel, but he was looking for a method to more easily switch between the two modes. Why would you want to do that? In some cases, software that was written to run on PAL may not work properly on NTSC, and vice-versa. The manual modification requires swapping out the VIC-II chip (MOS 6567 for PAL and MOS 6569 for NTSC), the timing crystal (17.734475 MHz for PAL and 14.31818 MHz for NTSC), and then changing jumper settings on the motherboard so that the C64 knows in which mode it should be running. So, Christian posed the question, “What if we could switch all of those modifications at once, with both options installed?” We began discussing ideas and sketching ideas on how to make this happen, given the technical and physical constraints of the types of C64 machines people would be installing our solution into. I built a dozen versions of this board before we settled on the final one, meandering between a logical digital switching solution, to a mechanical switch (literally a 10p2t push switch), to the final analog relay solution. We also went through both through-hole and SMD versions of many of the components, settling eventually on a solution that could be hand-soldered by most semi-technical enthusiasts.

The journey from that original sketch to a fully working 1.0 version took about eight months of part-time work. Christian was very patient with me as I tried (and failed) to get individual portions of the system to work. The solution is simple, but it’s not perfect. We would prefer to have gotten the digital switching option to work rather than use analog relays, and that a mechanical toggle switch doesn’t have to be used, as that implies that either a hole be drilled in the case, or a “pig-tail” with the switch attached dangle out an already-exposed hole in the rear of the case. The solution also requires a bit more modification than most casual C64 users may want to undertake. While we’d love this to be a simple plug-n-play solution, it is not… RF shields must be desoldered and removed, components and jumpers must be desoldered with pins soldered in to replace them… this is not as simple as plugging in a cartridge.

Details

Full details are available at Perifractic's Retro Recipes page.