Watford produced two VIDC Enhancers based on the same PCB. Both of these devices were controlled by the I2C protocol and only differed in the fact that one contained only a 36MHz oscillator and the other contained both a 25.175MHz and 36MHz oscillator.
I've fully documented the 36MHz version of the Watford Electronics VIDC Enhancer on its own page.
The photo below shows a variant of a VIDC Enhancer which is mounted in a similar way to the Watford Electronics VIDC Enhancer in an A410/1. The enhancer appears to be a 36MHz only model with the oscillator mounted on the underside of the PCB and the control chip mounted on the top side. The grey wire is the control wire which connects to the AuxIO connector.
The photo below shows quite possibly the smallest VIDC Enhancer ever made. The oscillator is on the underside of the PCB and the control chip is surface mounted on the top side. The device is a Beebug VIDC Enhancer. This VIDC Enhancer is fitted to an original Archimedes A440. The red and black wires leading off to the bottom left of the photo are the control wires which connect to the Aux IO connector.
More information about this VIDC Enhancer can be found on Chris Whitehead's site
Other VIDC Enhancer software can usually control only one extra VIDC clock speed and as such will only provide the same functionality with the Ultra VIDC Enhancer board.
The Watford Electronics VIDC Enhancer software only works with the WE VIDC Enhancer hardware and supports the "Standard" and "Super" versions of the board.
The 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.
!Modes replaces the standard desktop pallete feature with a more user friendly MODE switching facility.
!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.
NOTE: All these downloads are suitable for RISC OS based com