reDIP CIA MOS 8520 Modern FPGA Replacement for Amiga Computers and 1581 FD
reDIP CIA MOS 8520 Modern FPGA CIA Replacement Chips
For Amiga 500, 600, 1200, 1000, 2000, 3000, 4000, Amiga CDTV Computers and Commodore 1581 Floppy Disk Drive
Available Now at : ToTs RETRO
reDIP CIA MOS 8520 has been tested with a Amiga 500, Commodore 1581 Floppy Drive, BackBit Chip Tester Pro, Amiga Test Kit, VATest Program and has scored a perfect 100% passing mark.
The reDIP CIA is an open source FPGA board created by: Dag Lem, a prominent coder in the Retro Commodore Community who's work is also featured in VICE 64 emulator. This chip combines the following in a DIP-40 Package.
- Lattice iCE5LP1K-FPGA
- 1 Mbit FLASH
- 5v tolerant I/O
- Low Power Consumption
The reDIP CIA Provides an Open Source hardware platform for MOS 8520 CIA Replacements.
- The board is fully pin compatible with the venerable MOS 8520
- Cycle Accurate emulation of the MOS 8520 has been implemented with very accurate TOD
- Gateware implementation made possible by Frank "androSID" Wolf and Dieter "ttlworks" Müller
Note For Commodore 1581 Floppy Drives
When installing this in a Commodore 1581 Floppy drive, Capacitor c20 also needs to be changed. Included with this a 100uF -16v Capacitor to swap out with the c20 47uF-16v capacitor. Since the reDIP 8520 uses significantly less current and initialized faster than the MOS 8520, this capacitor is needed in position c20 for the drive to boot up on its own.
Do you technically need to install the capacitor? No, you can continue to use the 1581 drive with the new reDIP 8520 and original capacitor, however, you must turn on your floppy drive first and then your computer. In that order.
Amiga's do not need this modification and the reDIP can be used as is.
The repository for this open source project can be found here: on GitHUB
This product has been made available under:
CERN Open Hardware Licence Version 2
Copyright (C) 2025 - 2026 Dag Lem
Any Questions Please Do Not Hesitate to ask.