On 2017-02-20 08:26, groepaz@gmx.net wrote: > On Monday 20 February 2017, 08:19:57 Gerrit Heitsch > <gerrit@laosinh.s.bawue.de> wrote: >> On 02/19/2017 11:47 PM, HRSFALVI Levente wrote: >>> Another addendum: Marko once measured the luma levels of different >>> VIC-II chips in the same C64 motherboard, >>> http://www.zimmers.net/anonftp/pub/cbm/documents/chipdata/656x-luminances. >>> txt> >>> . I don't know how well the data practically holds, since the >>> >>> measurements have been done without using a standard 75 ohm load; yet, >>> one thing seems to be sure: there are slight differences between >>> different VIC-II chip revisions in the luma levels they produce. Maybe >>> part of what I've seen has been a result of that. I can't speak of the >>> other symptoms, I didn't make measurements myself. >> >> We have to remember that VIC is a bit of a mixed signal chip, it is >> mostly digital, but also produces analog signals. I take it as a given >> that there will be slight differences between VICs of the same revision, >> even if they come from the same wafer, let alone from different >> production runs where the process was tweaked over time. >> >> So measuring luma levels only counts if you have multiple VICs of each >> revision you can compare against each other. > > indeed, some other ppl checked the luma levels in the past decades, and its > always slightly different :) > The question here would be IMHO whether there is a correlation between VIC-II revision numbers and the luma maps the respective chips produce. The rest (general phenomenon of output level variances of mixed signal chips, general statements about measurement variances due to people measuring video signals with different / generally inadequate equipment etc. etc. etc.) is obvious. Levente Message was sent through the cbm-hackers mailing listReceived on 2017-02-20 09:00:02
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