The SX-64 to DX-64 Conversion Project

Introduction

Welcome! This project is an attempt to create a "Commodore DX-64" computer by adding a second drive to a standard SX-64 computer. There were only a few real DX-64 machines ever made as prototypes, and there is some debate about how the dual drives functioned. On the SX-64 the drive is labelled "Drive 0" and the empty slot is labelled "storage". One might assume on a DX-64 that the second drive would be labelled "Drive 1". This would lead us to believe that the internal drives behaved like the old Commodore 4040-type dual drives, where there is ONE device number (ie: device 8) for both drives, and each is accessed using D0 and D1. That would suggest commodore had a dual-drive FDD controller board. However, no evidence I am aware of supports this, so in all likelyhood the drives were setup to be accessed as TWO device numbers, example DRIVE 8 and DRIVE 9.

This project assumes separate drive numbers. This is means we can build a "DX-64" by "simply" adding a second FDD controller board and drive mechanism.

If you are the lucky owner of a REAL DX-64 please contact me!

Parts Needed

• SX-64 FDD board
• SX-64 drive mechanism with cable
• Replacement FDD power connectors (see below)
• Y-Cable for FDD power (see below)
• Y-Cable for FDD reset
• Y-Cable for IEC data (see below)

Construction

The construction pictures are currently hosted on Flickr. Please check here

Things to watch out for:

• The second drive will fit however the metal bracket is not designed for two drives. There will be a gap. Use spacers.
• The cartridge port will need some work as the second drive will push against it. Removing the bracket holding the IO card will allow extra room. The cartrige port will have to be rotated 180 degrees, or the plastic will need trimming.
• There is very little room available for the second FDD controller card. The power feed area will have to be modified. The metal shield will need to be removed and insulation installed.
• For best results the power connectors on the FDD boards will need to be replaced and a "Y-cable" built to feed power to both boards. An alternative is to hard-wire the two boards together and use one existing connector (this is what I did)
• You need to connect the data feed to the second FDD board. A standard SX-64 has TWO feeds from the IO card... one to the FDD board and one to the rear external ports board. If you don't need the external drive connectore then you can use the one to the rear board (like I did). Otherwise you will need to build another "Y-cable".
• Lastly, there are some concerns that the power supply is not up to handling two drives. My unit was, but it's possible that very early units might not.

Status

COMPLETED! Started Oct 16th, 2008 at 1pm and was completed at 6pm the same day.

Contact

Last updated: Oct 20/2009, 12:00pm EST

Send comments or feedback to Steve Gray(sjgray@rogers.com)