AutoVIDC - VIDC software control

Improving monitor compatibility and delivering higher screen resolutions
for the Acorn Archimedes range of computers.

AutoVIDC is a small piece of software that runs on RISC OS primarily to control a VIDC Enhancer although, that isn't its only job!

What is a VIDC Enhancer?

A VIDC Enhancer is a small piece of hardware that allow older Archimedes computers to deliver higher resolutions and improve support for modern monitors by providing a set of alternative clock speeds to the VIDC chip allowing it to run faster. By running the VIDC chip faster, you can enhance the video display capabilities of the Archimedes to match those of later models such as the Acorn A5000.

An Acorn BBC A3000 with VIDC Enhancer displaying a VGA screen mode

About AutoVIDC

Originally written by Andreas Barth in 1995 and now developed and maintained by Paul Vernon, AutoVIDC is unique amongst VIDC Enhancer software solutions in that it supports all known methods of setting the VIDC clock speed using either the Aux IO pins (for Atomwide and Beebug style VIDC Enhancers), the I2C bus (for Watford Electronics VIDC Enhancers) or the native Acorn VIDC Enhancer as built in to the later Archimedes A540, A5000, A4000, and A30x0 machines.

AutoVIDC replaces the bespoke software that was supplied with each different VIDC Enhancer (and usually targetted RISC OS 2). Through AutoVIDC every standard RISC OS screen mode that is provided by RISC OS from version 2.00 to version 3.11 is fully supported. Custom screen modes aren't forgotten either and they are supported through the creation of "Native" style screen modes using CustomVDU v1.71.

Standardised VIDC clock selection API

AutoVIDC also provides a full RISC OS SWI to deliver a standardised way of setting the VIDC clock speed for programmers regardless of the type of VIDC Enhancer fitted. This SWI is currently being used by the module LCDGameModes written by Steve Harrison which fixes many games that do not run correctly when an Archimedes is connected to a VGA or SVGA monitor.


AutoVIDC is designed to run on any Acorn Archimedes computer that has a VIDC1a chip fitted to it. As part of the initialisation process of AutoVIDC, the VIDC1a chip is detected and AutoVIDC gracefully exists if it is not found.

AutoVIDC has been tested on the following computers using a variety of versions of RISC OS:

AutoVIDC has been tested with the following VIDC Enhancers:

AutoVIDC should work (but has not been tested with) the following VIDC Enhancers:

The Atomwide and Beebug VIDC Enhancers are both Aux IO based designs so should work in the same way as other AuxIO based designs. The W.E. "Super" VIDC Enhancer is based on the same PCB as the "Standard" VIDC Enhancer and again should work in the same way as the "Standard" board does.

Known Incompatibilities

Where no VIDC Enhancer is fitted, AutoVIDC "assumes" an Aux IO based VIDC Enhancer is present. If other hardware is using the Aux IO pins, AutoVIDC could interfere with the correct operation of that hardware.

To my knowledge, there is only one piece of hardware that used the Aux IO pins which isn't a VIDC Enhancer. It is called IICAlarm and was created by Andreas Barth.

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Ultra VIDC Enhancer software

DownloadsThe Retro-kit Ultra VIDC Enhancer board uses the Aux IO connection in a slightly different way to previous VIDC Enhancers and requires AutoVIDC v2.00+ to be controlled in full. As of v2.07, AutoVIDC also supports WE VIDC Enhancers too.

The disc image contains the RISC OS 2 and RISC OS 3 versions of !CustomVDU and the !Modes application as well.

Related software

!Modes replaces the standard desktop pallete feature with a more user friendly MODE switching facility.

  • !Modes - Replacement MODE selector for the Iconbar (Spark archive)

!CustomVDU can be used to create custom screen modes and can automatically control all the Ultra VIDC Enhancer features with the exception of the over-clocking functions which require a small amount of manual configuration. This release is the latest 2013 release which is version 1.71.

  • !CustomVDU - Create custom screen modes (Spark archive)

NOTE: All these downloads are suitable for RISC OS based computers only.

Download LCDGameModes

Download LCDGameModes

LCDGameModes has now entered public BETA and is available for download.