Description
Give your RC2014 the cool graphics of the 80s. Based on the V9938 VDP (the lower cost predecessor of the V9958).
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 V9938 Video Display Processor (VDP) which powered the MSX2 line of 8 bit Z80 computers.
This kit is an alternative to the V9958 based RGB Mode. Its based on the lower cost V9938. See below for the key differences between the 2 Video Processors.
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 V9938 chip, was produced by Yamaha in the late 80s and was a backwards compatible VDP to TI’s TMS9918. It preceeded their V9958 VDP. 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
| Description | Yellow MSX Version | Green Stegosaur Version |
|---|---|---|
| Max VRAM on main board | 128K | 64K |
| VRAM Expandable? | No | Yes (up to 192K) |
| V9958 and V9958 Support | Single PCB can support both VDP types | Different PCB needed for each VDP type |
| V9958 WAIT signal supported | Yes | No |
| RGB Video output design | unchanged | unchanged* |
| Optional 5V out via RGB Connector | Yes | No |
| PCB Height | 8.0 cm | 5.5 cm |
| Colour | Yellow | Green |
* The Green Stegosaur RGB kit utilizes separate PCB designs for the V9938 and V9958 VDPs.
V9958 vs V9938
The following table highlights some of the key differences between the 2 chips.
| Feature | V9938 | V9958 |
|---|---|---|
| Max Colors | 256 colors simultaneously | Up to 19,268 colors (via YJK modes) |
| Hardware Scrolling | Vertical scrolling only | Both Vertical and Horizontal scrolling |
| Light Pen / Mouse | *Supported via Pin 26/27 | Removed |
| Composite Video | *Built-in output encoder on Pin 21 | Removed |
| DAC Power | Single power pin | Seperate power pins for logic and DAC |
* Mouse and Composite video are not implemented on the V9938 PCB.
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 V9938, 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 V9938 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:
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