Friday, April 21, 2017

V9938 and Videotex

Search for hidden MSX devices is like follow a breadcrumb trail composed of old magazines, small pictures in auction sites, ancient web pages, rumours in forums, etc. And the trail sometimes deceives us.

Even the search for MSX Video Titlers, which were easier to look for and their existance was known by the MSX community, gave some bad surprises.

To make the search process a bit worst,  the definition of a MSX based system is not the same between different people, so while someone believes that a machine with a V9938 and a Z80 is a MSX based appliance, the definition in use by this blog states that the candidate machine need run an unmodified (or slightly modified) MSX BIOS. Then we hit the definition of "slightly modified", and so on.

One of the bread crumbs that brought many failures is this small excerpt from "V9938 MSX-VIDEO Technical Data Book":
"CAPTAIN terminals and NAPLPS terminals using the V9938 have already been developed. We hope that the V9938 will be a standard video processing device on a worldwide basis."

You can know more about CAPTAIN here, and about two CAPTAIN terminals in these other posts. If you are lazy and need those informations in condensed form:

  1. Videotext was some kind of "Internet";
  2. CAPTAIN was the Videotext system in Japan, created by NTT;
  3. There is at least one CAPTAIN terminal that is a MSX computer and;
  4. At least another one that isn't.

Coming back to V9938 technical document, NTT is the only company which was thanked nominally by ASCII:

 "Finally, we would like to express our deep gratitude to the people at
NTT as well as the other related manufacturers for their valuable
opinions which contributed to the development of the V9938."

What interest NTT would have in a Video Processor development?

We know that a MSX1 can be a videotex terminal, as they actually were used by Telesp, one of the state owned Brazilian telecommunications company (which now is part of a Spanish group, Telefonica). The Telesp's videotex, called "Videotexto", was compatible with the videotex system used by France and many other countries, the Antiope.

Antiope is a system defined in the seventies, so it's graphical capabilities are from this era: 40 characters per row and 24 rows. Each character can have a background and a foreground color from a eight colors palette (but most terminals are B&W). Using a set of semi-graphical characters, you can have a screen resolution of 80 x 72 "pixels". Some later implementations can redefine the characters to emulate a higher resolution.

While the TMS9128, another son of the seventies, and his cousins are compatible with the Antiope specifications for Videotex, they aren't capable of all the requirements for advanced high resolution graphics like the ones needed by NAPLPS and NTT CAPTAIN.

In the article "Video Display Processors Draw the Line on Expensive Graphics Systems" in the 1984's "Mini/Micro Northeast Conference", Ron Peterson shows the main limitations of VDP from Texas:

"The TMS9128 has 3 architectural constraints which limits its compliance with NAPLPS:

1) A resolution of 256 x 192 pixels instead of the minimum NAPLPS SRM resolution of 256 x 200 pixels.
2) The TMS9128 does not have a full color bit map. Therefore, problems occur when there are more than two colors in a 1 x 8 pixel block on the display
3) The TMS9128 has only 15 colors; the NAPLPS SRM requires the display to be able to handle 16 colors from a palette of 512."

NTT CAPTAIN System had similar minimal requirements for their terminals, as we can see in this table from "Videotex Terminal Based On Personal Computer":

Pattern Terminal 204V x 248H Both characters and figures are transmitted as "pattern". (photographic transmission only)
2 Hybrid Terminal 204V x 248H Characters,marks,and mosaics are displayed at high speed using code transmission. Figures are displayed as "pattern".
3 High Resolution Hybrid Terminal 204V x 496H
408V x 496H
High resolution version of the Rank 2 terminal
4 Command Terminal 204V x 248H NAPLPS like geometric figure display is possible in addition to the Rank 2 terminal function

The V9938 overcomes all three "architectural constraints" of Texas VDPs:

  1. With 212 pixels of vertical resolution, the V9938 handles the CAPTAIN requirements (204 pixels) and still have enough space on screen to have a text row with status or navigation information. As NAPLPS SRM needs a lower vertical resolution than the CAPTAIN, it's also supported by the V9938.
  2. The V9938 have bitmap modes. Many. With different resolutions and amount of colors.
  3. By last, talking about the amount of colors, one of the V9938's bitmap modes supports 256 simultaneous colors and others have 16 colors from a 512 palette, exactly the same characteristics specified by NAPLPS (CAPTAIN asks for 16 simultaneous colors, but AFAIK it's from a 4096 colors palette).

The "Thanks to NTT" and those technical specifications are strong evidence that the V9938 was *created* to be used in videotex terminals. As a bonus, it can be used in Teletext terminals;  the teletext systems usually have the same technical specifications for screen resolutions and colors of their videotex equivalents (e.g.: NABTS is the Teletext version of NAPLPS).

That made me search and buy many CAPTAIN devices and communication terminals. Those buys were the worst spent money in my search for hidden MSXs. I got many CAPTAIN terminals but the only one in this list that have the V9938 video processor is the NTT Captain Multistation, and this one is not a hidden MSX! Some units even have the MSX logo!

Some CAPTAIN and Communications Terminals

The Zeal E/PASO didn't have a V9938, but a V9958, the same video processor used by MSX2+ and MSX TurboR. But, as we show in a previous post, even while the E/PASO shares the Z80-compatible CPU, the S3527 MSX-SYSTEM and the V9958 video processor with MSX computers, it didn't have the MSX architecture and can't boot the MSX-BIOS without hardware and/or software modifications.

And I am still in the search of the CAPTAIN and NAPLPS terminals mentioned in "V9938 MSX-VIDEO Technical Data Book".

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