From: Marko Mäkelä (marko.makela_at_hut.fi)
Date: 2002-04-07 17:44:37
Richard Atkinson wrote: > Although the Oric video chip is quite interesting in itself Yep, the video chip definitely makes the Oric the Spectrum of the 6502 world. Without hardware modification, it's almost impossible to write a raster interrupt routine. (I say almost, since one probably could observe the memory access patterns of the video chip by reading from unconnected address space (if the Oric has anything like that).) The funny thing about the video chip is that it has no memory-mapped registers. It is entirely controlled by the contents of the video memory. Some sort of a "textual frame buffer" device, or similar to Ceefax or Teletext chips. This is a good thing for hardware hackers, since the video chip will always come up with a picture, even if the processor does not work. > It uses a MOS 6522 VIA to control the PSG data, address and control > busses with some very interesting hacks resulting from this method > of controlling the PSG. Could the slightly audible distortions from the internal speaker while trying to load from tape be caused by this? Marko Message was sent through the cbm-hackers mailing list
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