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Nuevo artículo: interface de video MSX para Spectrum |
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Sábado, 11 de Octubre de 2008 16:03 |
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English version is in progress. By now there's only a spanish version of this article, with a Google translation version attached to each section. Reading english this way is odd, but at least you will get a general idea of what's this interface is about. I hope to release a "better english" version soon.
Después de haber estado un tiempo sin actualizar la página, por motivos laborales, publico un artículo que se escribió realmente hace ya unos meses, dado que la revista online donde iba a publicarse, al final ha decidido no hacerlo.
El artículo describe una interface que se me ocurrió realizar a principios de este año. Cayó en mis manos un artículo sobre la representación de gráficos en la época de las máquinas de 8 bits. En ese artículo comparan las diferentes técnicas que han implementado los micros más populares de la época.
La lectura de ese artículo me llevó a investigar un poco cómo otros micros habían salvado el escollo que supone tener a dos elementos del ordenador accediendo simultáneamente a la memoria de pantalla. Sabía de sobras cómo lo hace el Spectrum, algo ya sabía de cómo lo hace Amstrad, y en el artículo hablaba de cómo se resuelve en el C64. Así que el siguiente en mi lista era el MSX.
Cuál no sería mi sorpresa al comprobar que el chip de video de MSX es sólo un periférico más, que sólo expone dos puertos de I/O al procesador. "No puede ser tan sencillo" me dije, así que pregunté en los foros de programación de CEZ y confirmé mis sospechas: el chip de video del MSX es sólo un periférico más.
El artículo, en español esta vez, describe cómo funciona el TMS9929, chip de video PAL de los MSX-1, cuenta qué cosas han tenido que tenerse en cuenta para la adaptación de este chip para el Spectrum, cómo puede programarse desde BASIC usando IN y OUT, y algunos ejemplos de conversiones de minijuegos o demos de MSX, de los cuales he podido obtener el código fuente.
Enlace a la página inicial del artículo. También disponible una versión en PDF. |
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A PoC for a full resolution, full speed (25fps) movie player for the ZX Spectrum |
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Lunes, 07 de Julio de 2008 19:23 |
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How is this possible? Previous research in this subject had been made by "decicoder" (an active member of the OTLA project) that led to the Zinetrix program, which was bravely able to load a series of screen$ at a very high speed, giving the illusion of movement (instructions in spanish).
This topic has been discussed at WOS forum also. Some members have shown some demos of what seems to be videos "downgraded" to the speccy resolution and later played on a PC/Mac.
What I want to show to you it's a real and humble Spectrum 48K playing a 2 minute video, at full resolution (256x192) and full speed (25 fps). Needless to say that this comes with a little help named... DivIDE.
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A replacement for the internal speaker |
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Viernes, 27 de Junio de 2008 02:32 |
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The Spectrum internal speaker is not a robust manufactured one. The two tiny wires that come from the inside are directly soldered to the outer pads, that in turn are soldered to the pins that go to the PCB. This means that a rework on this pads may lead to wire brokerage and thus, rendering the speaker useless.
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The oddities of the Inves Spectrum+ |
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Jueves, 17 de Julio de 2008 23:45 |
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The Inves Spectrum+ (link provided by Zonadepruebas) was a Spectrum 48K clone made by Investronica, the spanish partner of Sinclair Research, and responsible for Sinclair distribution in Spain.
This clone has suffered from numerous incompatibilities, mainly because of its non standard ROM, altered in some ways, mostly of them to comply with spanish regulation, that demanded that every computer with less than 64K had to be "spanished". That is: error messages had to be in spanish, and the keyboard and screen had to be able to display some spanish characters, like Ñ, ¡ and ¿
Among the features of the Inves Spectrum, there was one that we can consider "unique" on the history of Sinclair computers: the Inves Spectrum was presumely the first Spectrum clone that could be damaged permanently by issuing instructions...
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Where does that noise come from? |
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Martes, 17 de Junio de 2008 00:28 |
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This is a ZX Spectrum 48K, issue 6A, from ZXevious. He asked me for advice on how to repair its speccy. Came with a faulty Interface 1, which I speak about in another article.
Upon switching on, the screen shows flashing blocks, hangs, and the screen data is mixed with something that seems digital noise. Maybe from poorly coupled data lines.
ULA is operational, Z80 too, so the main candidate is low memory. First thing is to try to isolate which memory chip (or chips) are damaged. The usual cartridge ROM tests I ran didn't give a clue, as it seemed that every chip was damaged. Strange enough that all power lines were ok.
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