GlitchGuru & GadgetArchivist
GlitchGuru GlitchGuru
GadgetArchivist GadgetArchivist
GadgetArchivist GadgetArchivist
Hey, I’ve been digging into the old Commodore 64 and I found a hidden test mode that unlocks a bunch of undocumented routines. I think it’s a neat puzzle for us to crack together—any chance you’ve seen it before?
GlitchGuru GlitchGuru
Sure, that sounds like a classic hunt. Which routine set are you looking at? Let's dig into the memory map and see what oddities pop up.
GadgetArchivist GadgetArchivist
Sounds like a good plan. I’m staring at the $0100–$02FF region, that old system variable area. The routine I’m hunting for starts with the bytes D9 6D, then a 0A loop that looks like a hidden stack dump. I’ve marked the spots with tiny sticky notes in the old notebook I keep for these finds. Let’s pull up the ROM dump and see if we can cross‑reference the opcodes with the classic docs from the 1985 compuserve archive. That should give us a clue about the hidden test mode. Ready to dive in?
GlitchGuru GlitchGuru
Yeah, let’s load that ROM dump, set a breakpoint at $0100, and watch how the D9 6D bytes start moving that stack pointer. We’ll track the 0A loop and see if the compiler prints any debug output in the hidden mode. Let's get the 1985 archive docs ready so we can cross‑reference the undocumented opcodes and spot any signature patterns. The deeper we go, the more quirks we’ll find. Let's dig!
GadgetArchivist GadgetArchivist
Okay, I’ve got the ROM loaded and the breakpoint set. I’ll keep a close eye on the stack pointer as those D9 6D bytes shuffle it around. The 0A loop looks like a quick counter, probably part of the hidden diagnostics. Pull the 1985 docs, and I’ll compare the opcode fingerprints to spot any off‑beat patterns. Let’s see what secrets this old machine is hiding.
GlitchGuru GlitchGuru
Got it—loading the docs now. While you watch the stack pointer dance, I'll flag any opcode sequences that don’t match the official list. Those outliers could be the real clue. If the hidden mode triggers a unique routine, we might see a self‑referential jump or a checksum check that never runs in normal mode. Stay ready, the C64 loves to hide its secrets in plain sight. Let's see what weirdness we unearth.