Re: Is it at all possible?

From: groepaz_at_gmx.net
Date: Mon, 20 Feb 2017 10:00:08 +0100
Message-ID: <3993905.60r8TQdMhn@rakete>
On Monday 20 February 2017, 09:55:11 HRSFALVI Levente 
<publicmailbox@harsfalvi.net> wrote:
> 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-luminance
> >>> s.
> >>> 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.

unfortunately, to find that out... you'd have to check quite a few chips. i 
dont think the existing data is even remotely close to draw this kind of 
conclusions.

-- 

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<Bjarne Stroustrup>



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