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Guimauve 2ooo is a simple adapter board that plugs to the rear side of an Apple //c computer,
and produces either a monochrome (black and green) or color display on any VGA monitor.
You only need a standard VGA cable and a pair of PC loudspeakers for sound output.
No power supply is required, as the Guimauve 2ooo board is powered directly by the Apple //c computer.
A small switch placed on the board allows you to choose either a color output, or a monochrome output, at any time. The black-and-green display mode has been created because many people used their Apple //c computers in conjunction with the famous little monochrome monitor especially designed for it.
The name "Guimauve" has been chosen due to its vague resemblance with the "Chat Mauve" name. Chat Mauve adapters were popular in France, as they allowed to connect your Apple //c computer to any TV featuring a SCART connector.
This board has been designed by Gregory Estrade, a.k.a. Torlus, for the Silicium computer museum.
The board design has been directed by many objectives. One of them was to have a board easy to build and assemble, as all the manufacturing process is performed by people at Silicium. We also wanted to keep the cost as low as possible.
For these reasons, the board suffers from limitations, especially on the color display modes. Color rendring on the early Apple computers is a somewhat tricky process, and emulating it properly would have required a consequent amount of logic, which would have been against our primary objectives.
The monochrome rendering, on the other hand, is pixel-perfect, both in 40 columns and in 80 columns modes.
Depending on what you're looking for, this board may fit your needs, or not. If you're planning to make an extensive use of the color mode, please watch carefully the pictures below, and decide by yourself if the color mode rendering is satisfying enough for you.
Attention owners of European Apple //c computers: the board follows the vertical refresh rate of the Apple //c.
It means that if your Apple //c has been manufactured for European market, then it probably features a vertical refresh rate of 50Hz, whereas VGA standard is 60Hz.
It means that the board is not designed to work on these computers. However, some VGA monitors can cope with a vertical refresh rate of 50Hz,
and with a slightly different firmware, it is still possible to use the adapter. However, we offer no warranty about this.
Please keep that in mind if you're still interested in purchasing one board.
If you are unsure, please don't purchase it, as we don't want to deal with returns and refunds.
Price is EUR 75, or USD 115, shipping included. To order, please send an e-mail to guimauve@silicium.org.
We accept PayPal for the payment. Expect a delivery time of 2-3 weeks, as we're manufacturing the boards on our (scarce) spare time.
If you are an European customer, please read carefully the notice above, and don't forget to mention it in your e-mail, as the board needs to be programmed with a different firmware.
The adapter acts like a scandoubler, and performs 15Khz to 31Khz video signal conversion. The scandoubler design has originally been made by Stephen A. Edwards, for his Apple2fpga project.
I adapted his design to use a CPLD and an external SRAM chip, instead of a FPGA.
Basically, while an Apple //c scanline is sampled and stored in a RAM buffer, the previously sampled scanline is rendered off another RAM buffer 2 times (31Khz vs 15Khz).
For color rendering, a simple two stages R/2R ladder is connected directly to the CPLD outputs.
Here are some photos of the video output produced with an Apple //c computer and the adapter, both in color and monochrome modes. They will hopefully help you to judge the rendering of the color output.
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