🛠️ In this video, I demonstrate how to use a 6502 processor as a replacement for the harder-to-find 6504 in Commodore IEEE-488 disk drives like the 2040, 3040, and 4040 series.

💡 If your 6504 fails, this solution could save your drive from becoming an enormous and over-the-top paperweight.

What’s in the video:

  • 🧩 Comparison of 6502 vs 6504 pinouts and specifications
  • 📋 Explanation of the key differences between these processors
  • 📝 Schematic for the conversion solution
  • 🔍 Close-up look at the adapter
  • 🧪 Testing the solution on my recently repaired 3040 drive

If you’re having problems with a 2040/3040/4040 disk drive, check out my new diagnostics ROM:

📂 GitHub repo: https://github.com/piersfinlayson/cbm-ieee-disk-diag-rom

Timestamps

00:00 Introduction
01:13 6502 vs 6504 pinout
04:14 Breakout board schematic
05:09 The breakout board
06:18 Testing it
07:32 Wrap-up

Video content copyright (c) 2025 piers.media Limited. All rights reserved.

comments powered by Disqus