Iz8dwf celebrates reaching 1,000 subscribers, thanking the Adrian’s Digital Basement channel for support. He quickly introduces the main topic: NOP generator troubleshooting for 8-bit CPUs. This technique helps anyone working with MOS6502 and Z80 chips, whether in classic computers or arcade boards.
How NOP Generator Troubleshooting Works
A NOP generator forces a CPU to execute only NOP instructions, cycling through all address lines in sequence. If the address and data buses work, the address progression stays clean and steady. If you notice erratic bus activity, you have a hardware issue. Faulty ROM selection or multiple chips fighting over the data bus cause the CPU to freeze or fail.
Making and Using Socket Adapters
Iz8dwf shows how to build a NOP generator with a 40-pin socket. He hardwires the data bus pins so the CPU always sees a NOP instruction. Cutting and soldering specific pins prevents unwanted signals and interrupts. He also adds resistors for extra safety, protecting the data lines from electrical conflict.
You only need basic tools for this method: a logic probe and a frequency counter. With them, you can check if the address lines and buffers toggle as expected. If you see an output missing or out of sync, you’ve found the fault.
Step-By-Step Demonstration
The video features a live test on a Commodore PET 2001 motherboard. Iz8dwf checks address lines, buffer outputs, and decoders. He shows exactly what to look for with the logic probe. Each address line should toggle at half the speed of the previous one. Decoders must only select one output at a time. These signs mean the logic is working.
He points out a limitation with the 6510 CPU, found in the Commodore 64. This chip’s special I/O registers at addresses 0 and 1 make NOP generator troubleshooting tricky. The CPU may run a BRK routine instead of cycling through memory. So, this approach is less useful on the 6510 than on the 6502 or Z80.
Adapting for Other Chips
Z80 processors work well with this method. Tie all data pins low and cut interrupt lines. Other CPUs, like the 6809, require similar steps, but always check the pinout and datasheet. Iz8dwf encourages viewers to adapt NOP generator troubleshooting to their hardware, staying flexible as they repair.
Watch the Full Video for Details
Iz8dwf delivers technical advice and practical demonstrations throughout the video. Viewers who work with classic computers or arcade boards will save time using these methods. His step-by-step guide lets anyone test and repair address or data bus issues with confidence. If you want a clear, direct repair technique, NOP generator troubleshooting is a must-watch.
