On 2013-05-02, at 22:16, silverdr@wfmh.org.pl wrote: > I had a moment of inspiration today (after Michau asked about the SX ROMs) to check how it is done in the SX (I thought it was like in the older 64s) and.. it occured that there are actually /two/ crystals piggybacked one on another and just three 74LS chips next to the passive stuff on the daughterboard called "clock unit". This means much more "generic" solution than the 8701, which I try to get rid of and even better in this terms than the hard to come by chips from the "discrete" clock generator in earlier C64 boards. I went even further and dragged all my SXes out of the closet to see if they are still capable of displaying something and check the picture on the proper display. Seems that the SX (doesn't have the RF modulator) has quite sharp output, which normally is not really to be appreciated on the internal screen. Interestingly though for every colour that has a chroma content (i. e. is neither black nor white nor any of the three shades of gray) the scan lines are "pixelated". Meaning the level of the luma varies from pixel to pixel (or more than one pixel - haven't counted/measured so can't say now exactly how wide the period of this wave is but looks close to two pixels) creating various patterns in place where a solid colour would be expected (at least horizontally). Various, because it seem to depend on which colour is actually selected. For example the cyan colour generates a kind of vertical stripes (in addition to the horizontal ones caused by the scan lines), meaning that the phase of this variation replicates each scan line: http://dl.dropboxusercontent.com/u/58002657/sx64_picture_closeup_colour3.jpg Light blue OTOH seem to have the phase of this "signal" inverted every scan line, which makes a sort of alternating grid on the screen: http://dl.dropboxusercontent.com/u/58002657/sx64_picture_closeup_colour14.jpg I am wondering if anyone knows (before I start disassembling the SX in order to experiment) whether this effect can be caused by the differences in the clocks generation methods between regular 64 and the SX or something else (like the output amp). -- SD! Message was sent through the cbm-hackers mailing listReceived on 2013-05-03 00:00:03
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