Re: Is it at all possible?

From: HÁRSFALVI Levente <>
Date: Sun, 19 Feb 2017 23:47:22 +0100
Message-ID: <>
On 2017-02-19 23:07, wrote:
>> On 2017-02-19, at 22:45, HÁRSFALVI Levente <> wrote:
>>>> There is clearly a visible difference between an R3 and an R5 on a 250466 board. (I've been using an R3 after having killed the original R5 of the machine / before I could obtain another one.)
>>> Could you elaborate/describe the difference? It's been some time since I tried those (and it was not in the '466 either) but I didn't notice anything striking. The R1 with its luma levels makes a noticeable difference but the later ones?
>> Less contrast, more blurry / noisy / subjectively darker startup screen. Nothing as obvious as the 6569R1 with its fewer luminance levels, but still something clearly noticeable.
> Uhm in that case.. shall have to check again and try to do some semi-scientific measurements.

I should add that I always use CRT displays to play around with vintage 
gear (if I just have a chance). I observed the above on a usual CRT 
display, at the time probably a tv set from the early 90s.

Another addendum: Marko once measured the luma levels of different 
VIC-II chips in the same C64 motherboard, 
  . 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.

>> (Worst of all, with the R3 installed the machine started to exhibit VSP crash symptoms, which it never did previously.
> But that - again - doesn't have much to do with the parameters of the picture it generates.



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Received on 2017-02-19 23:01:13

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