Dragon DOS

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Dragon DOS 1.x

Dragon Data Ltd comissioned The Micro Works to write the original Dragon DOS, some pre-release examples of this including the (c) Micro Works signature can be found in the downloads area. Shortly after release a number of bugs were discovered in 1.0 and a number of articles were published in Dragon User with patches to the ROM code to correct the worst of these. The most common version is 1.0, it is not known if any other version was officially released although 1.7 has been seen but the source of 1.7 and the differences with 1.0 are unknown at this time.

Dragon DOS 2.x

For the Dragon Alpha a modified version of Dragon DOS was required, one that would load into RAM from disk rather than exist on a ROM. Vivaway Ltd were given the source code for Dragon DOS 1.x and Dragon DOS 2.x was created. A VDK disk image of Dragon DOS V2.F for the Dragon Alpha can be found in the downloads area. From looking at segments of the original Dragon DOS 2.C source code it would appear that Vivaway Ltd implemented the changes as options so that the source code could be assembled for a Dragon ROM or RAM implementation - There is also an option that appears to infer it would also assemble to work on a Tandy CoCo.

Dragon DOS 4.x

Eurohard wanted to release an updated Dragon DOS for the Dragon 64 / Dragon 200 that contained all the known bugfixes and to avoid confusion with the 2.x series numbering they jumped straight to V4.0. A ROM image of this is available for download.

Dragon DOS Interface Pictures

Dragon DOS IC Parts List

DragonDOS Board IC list (with Datasheets)

Part Number Description Datasheet
2764 8Kb EPROM (pdf)
SN7416N Hex inverter buffers/drivers with open-collector high-voltage outputs (pdf)
SN7417N Hex buffers/drivers with open-collector high-voltage outputs (pdf)
SN74LS00N Quad 2-input positive-NAND gates (pdf)
SN74LS04N Hex inverters (pdf)
SN74LS74AN DUAL D-TYPE POSITIVE EDGE-TRIGGERED FLIP-FLOPS WITH PRESET AND CLEAR (pdf)
SN74LS139N DUAL 1-OF-4 DECODER/DEMULTIPLEXER (pdf)
SN74LS174N Hex/Quadruple D-Type Flip-Flops With Clear (pdf)
WD2797PL-02 Floppy Disk Formatter/Controller (pdf)


New developments

Several people have created new versions of the DragonDOS controller, which use the same WD2797 floppy controller IC as the original controller but are smaller.

This one was created by Jose Leandro, a spanish Dragon user.

Full details (in spanish): http://hardware.speccy.org/temp/Dragon-1.html


  • Lafumat's Dragon Disk Controller (July 2012)

This one was created by Lafumat, an user of the spanish RetroWiki and Zona de Pruebas forums.

Dragon DOS Downloads