Retro-Kit Ultra VIDC Enhancer

The Retro-Kit Ultra VIDC Enhancer provides the ultimate in flexibility for older Archimedes computers delivering support for different monitor types and for the provision of higher resolutions, allowing you to transform your display capabilities through the use of multiple software-selectable crystals.

  • Acorn A3000 with a 15kHz CRT monitor
  • Acorn A3000 with a VGA monitor

The Ultra VIDC Enhancer is intended to work with version 2.00 of AutoVIDC and above and is capable of providing up to three extra VIDC clock frequencies in addition to the original 24MHz frequency that is native to the Archimedes itself.

As standard, the Ultra VIDC Enhancer is supplied with a 25.175MHz and 36MHz oscillator fitted to the board only. This leaves the option to add in a custom oscillator at a later date to overclock the VIDC chip if desired*.

The photo below shows an Ultra VIDC Enhancer configured and fitted to an A310 and it is suitable for the A300, A400 and A400/1 series machines.

An Ultra VIDC Enhancer fitted to an Archimedes A310

As you can see from the image, the design also incorporates the Sync on Green fix that is present in the original Retro-Kit single oscillator VIDC Enhancer thereby allowing the board to be fitted to older machines with the minimum of changes to the original Archimedes motherboard.


The Retro-Kit Ultra VIDC Enhancer sports the following features:

  • Low power, single chip, three oscillator design 
  • Compact design measuring 51mm x 36mm
  • High quality professionally finished PCB featuring a double sided design with 1.5oz. full copper pour to reduce signal interference
  • Less on chip signal processing required when compared to the previous design
  • Provides a reversible fix for FCO2022 using jumpers to control Sync on Green availability
  • Upgrades any older Archimedes to at least match the A5000's video output capabilities
  • Exceeds the functionality of a Dual VIDC Enhancer in a low profile, single board design
  • Can be left fitted to the machine regardless of the type of monitor attached
  • Does not obstruct the lower podule (Podule 2) slot allowing for co-processors.
  • Ability to over clock the VIDC chip allowing for screen resolutions up to 1024x768 *

Software control using AutoVIDC v2.00

AutoVIDC has been updated and features several enhancements over previous versions of AutoVIDC including:

  • Supports up to four VIDC clock frequencies
  • Fully automated and transparent software control
  • Automated enhancement of RISC OS 3 (S)VGA mapped modes
  • Specified MODE's can be ignored by the VIDC Enhancer
  • Extensive command line customisation features
  • Provides several SWI's for programmatic control by the user


The Ultra VIDC Enhancer is compatible with the A300, A400, A400/1 and A3000 series' of Archimedes computers and can be provided in two different configurations both of which are shown below.

Retro-Kit Ultra VIDC Enhancer - A300, A400 and A400/1 configuration

Retro-Kit Ultra VIDC Enhancer - A3000 configuration

Both configurations of the Ultra VIDC Enhancer are functionally equivalent. The missing components on the A3000 version are not required as the A3000 does not provide the Sync on Green signal which must be removed on the earlier Archimedes ranges when connecting to a (S)VGA monitor.

In the photo below, you can see an Archimedes A310 running RISC OS 2 on the left and an Archimedes A410/1 running RISC OS 3.11 on the right. Both machines are using MODE 31 (800x600@56.2Hz with 16 colours) desktops. MODE 31 is not normally available to RISC OS 2 at all and requires custom mode definitions to be added to the system for it to work. Whilst MODE 31 is available by default with RISC OS 3, it still cannot be achieved on the Archimedes prior to the A540 series without a VIDC Enhancer.

An Archimedes A310 and A410/1 both running MODE 31 using Ultra VIDC Enhancers

Development information

After being surprised by the level of demand for the original VIDC Enhancer, I began work on designing the Ultra VIDC Enhancer in late November 2012 with the thought that I would create a VIDC Enhancer that would deliver as much functionality as possible in a single board. By late December 2012 had a fully functional prototype laid out on a bread board.

Testing out the Ultra VIDC Enhancer circuit design

Having proved the viability of the design, the next stage was to formalise the schematic and create suitable PCB layout which I completed in the first week of 2013.

Due to the number of oscillators and potential for signal noise causing interference between the signals, I sent the PCB design files to Tecbridge circuits for the purpose of manufacturing a high quality PCB with full copper pour.

In late January, the completed PCB's arrived and the first Ultra VIDC Enhancer was assembled for testing and fitted to my Acorn BBC Archimedes A310.

* Over-clocking can introduce system instability or cause permanent damage to your computer hardware if done incorrectly. Use of the Ultra VIDC Enhancer to over-clock the VIDC chip is carried out entirely at the owners risk and Retro-Kit cannot be held responsible if you damage your VIDC chip or other hardware in the process.

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Pre-order your Ultra VIDC Enhancer now

I opened up a list of pre-orders in anticipation of creating a new batch of Ultra VIDC Enhancers in 2016. Due to delays, they're now going to be ready in July 2020. Please contact me to enquire about being placed on a pre-order list. No payment is necessary until the Ultra VIDC Enhancers are ready to ship.

A3000 Ultra VIDC kit

The anticipated price should remain the same at £32.50 each + £6.95 P&P to locations in the UK (other countries may incur greater shipping costs). The package includes the Ultra VIDC Enhancer, all connecting cables, headers and jumpers required for your Archimedes and a 3.5" floppy disc with the software on.

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.

Other VIDC Enhancer software

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.

Ultra VIDC Enhancer Eagle files

The Ultra VIDC Enhancer and Sync on Green board layout was created using Eagle PCB design software from Cadsoft and the project files can be downloaded below.

Acorn BBC A3000