The 1565 is an external floppy drive for the Commodore 65 computer. It is even rarer that the computer itself – only a few are known to exist. This project aims to create a fully functional replica of the drive.
Project status
Hardware: 100% complete.
Case: pending. If you can assist in designing and 3D-printing the case, please contact me.
Description
Unlike older 8-bit Commodore peripherals, the 1565 is a “dumb” drive, similar to Amiga drives. It contains only the drive mechanism and some simple support logic – the computer is fully responsible for providing all the control signals to the drive.
Unlike Amiga drives, however, the interface to the drive is serial, not parallel. Drive control signals are multiplexed on a single wire using computer-provided clock. The 1565 contains a custom 4101 chip which supports this serial interface, decoding the clock, reading the signals provided by the computer and sending back status signals. The protocol is described in detail in the Commodore 65 manual (chapter 2.6.2.):
http://www.zimmers.net/cbmpics/cbm/c65/c65manual.txt
The main goal of the project was therefore replicating the 4101 chip, which was done using 6 standard TTL chips. Almost all functionality of the original chip was re-created, with some minor changes:
- The drive used in 1565 supplies an additional signal “Disk Inserted”. This signal is not present on standard Amiga DD drives, therefore the replica drive always sends 0 instead (indicating that the disk is always inserted).
- For simplicity, the signal “Index” is also not sent.
- The original 4101 chip had inputs to select drive number (0-7), however the C65 firmware recognizes only one external drive, assigning it the number 1. Therefore the drive uses only the least significant bit of the drive number sent from the computer.
The replica drive has been fully tested with a Rev 2B Commodore 65 and works well except one thing: disk format operation fails on the external drive. It is unclear whether this is the limitation of the computer firmware (which is known to be buggy) or problem with the drive itself. Apart from that, the drive reads and writes disks formatted in the internal drive (or a 1581) without any problems.
The replica PCB is designed to fit in the original 1565 case. It is larger than the original PCB, but it fits well below the drive mechanism. The PCB accepts both standard Amiga or 1581 3.5″ drive mechanisms or PC mechanisms; however, testing was done mostly using Amiga drives.
To use the replica, you will need:
- The PCB (which you can get from me).
- A drive mechanism (standard F-354 Amiga drive is recommended).
- A power supply (the same as used in 1541-III / 1581 / CD-32 / C65).
- A mini-DIN8 cable (can be had from Ebay) – 1m length maximum.
PCB
Pending
Schematic
Pending
Purchase
Fully assembled and tested PCBs available. Contact me if you want to buy one.