What is it?

A complete kit to give your RC2014/RCBus platform, the advanced graphic capabilities of the mid to late 80s. It based around the V9958 Video Display Processor (VDP) which powered the MSX2/MSX2+ line of 8 bit Z80 computers.

The main PCB supports the installation of 64K of VRAM, sufficient for all screen modes of the processor. With the use of the optional expansion board, the VRAM can be extended to the full 192K of VRAM that the V9958 is able to address.

This kit is a derivative of the Yellow MSX V99x8 RGB Module. See below for table of differences.

This V9958 chip, was produced by Yamaha in the late 80s and was an update to the the V9938 chip, which was itself, a successor to TI’s TMS9918. The V9938/V9958 addressed many of the shortcomings of the original TMS9918.

Key features

• Compatible with RC2014/RomWBW.
• Support for 64K of VRAM on main PCB, or expanded to full 192K of VRAM with optional VRAM expansion module.
• RGBs via 15-pin DSUB/VGA connector.

Key difference with Yellow MSX RGB

* The Green Stegosaur RGB kit utilizes separate PCB designs for the V9938 and V9958 VDPs. This allows the V9958's PCB, to refine the layout and tracing of the power delivery components for the V9958's DAC; minimising, as much as possible, potential EM interference appearing on your display.

Output connections

You will want to think about how you plan to connect this board to your chosen monitor. The video signals produced by 80's hardware is not trivial to connect to modern LCD monitors. For such monitors you will need a converter to upscale the output. Although VGA Monitors can accept a RGB signal, they are unlikely to support the lower frequency of 15Khz produced by this module.

The RGBs module provides connection via the 15-pin DSUB/VGA connector. This output is well suited to connect via a VGA cable to a compatible HDMI/VGA up-converter that accepts a RGBs signal over the 15pin connection, such as the GBS-8200 or HD-VC9900 converters. For more information on the DSUB RGB/VGA see RetroRGB's VGA article

The RetroRGB upscalers article has a good description for some of the converter options.

Items such as retroTink and OSSC are very high quality converters - but also have a decent price tag.

I have found the low cost arcade converters such as the GBS-8200 and HD-VC9900 converters produce excellent results. The upscalers can be acquired through the usual ebay, amazon and other sellers at very reasonable prices.

The GBS-8200 can also be easily modified to produce more customised and higher quality output - again RetroRGB has it all explained at GBS Control

Upscaling Testing status

As per the Yellow MSX RGB module, I have tested this kit with the low cost GBS-8200 and HD-VC9900 upscalers. These have produced solid stable images for the respective VGA and HDMI output. They seem very tolerant of CSYNC voltage signal levels.

My recommendation is to use GBS-8200 or the HD-VC9900 upscalers. The quality is fine and I do most of my testing on these converters. Just google their codes and you will find the usual retailers/marketplaces (eg: ebay/amazon/aliexpress) have plenty of purchase options.

There are 2 revisions of the GBS-8200 available (V4.x and V5.x). The V5.x produces a poorer quality output. Recommend the older V4 revisions. You can identify the V4 revisions by the colour of the menu control buttons. Black for V4 and Yellow for V5.

Other upscalers, such as the OSSC and retroTink may work, but I am unable to verify and confirm. Your mileage may very. Adaptor cables would need to be constructed.

I have not tested the unit on a real RGB CRT monitor.

I have been advised by some builders of the Yellow version of this kit (which has an identical RGB output stage as this module), that they have successfully tested with a real CRT, the OSSC and retrotink devices.

What's included in this kit

The kit can optionally be supplied with individually tested V99x8 and 4164C chips. Or you can choose to exclude these chips if you wish to source them yourself.

The memory expansion board can also be optionally included.

Please note, that without the Expansion board, the module can only support 2 4164C RAM chips for a total of 64K VRAM.

Everything else you need is included (PCB, passive components, crystals, sockets, connectors and other ICs)

The ATF16V8 is supplied new and programmed for immediate operation.

What else do I need to make this work?

• You need a working RC2014/RCBus system (cpu, RomWBW, Clock, etc - enhanced bus required).
• This module can be used as a replacement for the Yellow MSX V99x8 RGB Module
• A compatible monitor or upscaler converter

Construction notes

Please note that due to the finer pitch pins of the V9958, the soldering of this board requires a little more finesse than the typical RC2014 through-hole based boards. If you have built a few boards already, then you should be fine. It's recommended that a finer pitch soldering tip be used as it can be easy to accidentally bridge some of the pins.

Extra care needed when inserting the V9958 into its socket - there are lots of pins, take your time to avoid bending pins.

For more notes and any revisions please have a look at main documentation page at:

https://www.dinoboards.com.au/stegosaur/v9958/

Disclaimer

Please note that this is a kit, produced by a non-professional (me) for hackers, DIYers' and retro lovers, to tinker with. I will do my best to answer any support questions you may have.

The V9958 and 41464C chips are obsolete and out of manufacture. They may be old-new-stock or pre-used, and as such there is a risk they may not function correctly. Therefore, I fully test each chip, in-circuit, prior to packaging, so you can have good confidence that the chips you receive will perform as required.

Normally shipped next working day, however during busy periods this may extend slightly.

It is your responsibility to pay any import duty or other taxes where appropriate, unless specified below:

For EU locations:

* Please see Lectronz's Terms and Condititions (https://lectronz.com/pages/terms_and_conditions)

* For order 150 EUR or over, it will be your responsibility to pay any import duty or other taxes where appropriate.

For USA:

A 20% Tariff tax is applied at checkout.

Tariffs are prepaid by me prior to shipping. You will not incur any additional tariff charges, upon receipt of your package.

For Australia:

Registered for GST. Prices are listed exclusive of GST. GST of 10% is applied at checkout.