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From: Unknown <dog@gmail.com>
Newsgroups: comp.os.linux.misc,alt.os.linux.slackware,alt.os.linux.debian
Subject: Re: Hk Cqvst wrote: nVidia + gamma !FIXED!
Date: Wed, 21 Jan 2015 11:59:01 +0000 (UTC)
Organization: A noiseless patient Spider
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Message-ID: <pan.2015.01.21.12.07.38@gmail.com>
References: <m9jf2n$pq3$2@dont-email.me> <m9m7sg$vs1$1@dont-email.me> <m9mgj2$3ag$1@dont-email.me>
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On Tue, 20 Jan 2015 21:16:18 +0000, Jerry Peters wrote:

> In alt.os.linux.slackware Avoid9Pdf@gmail.com wrote:
>> In article <m9jf2n$pq3$2@dont-email.me>, Rich <rich@example.invalid>
>> wrote:
>> 
>>> > xset s off
>>> > xset -dpms
>>> >      'fixed it' but before I die I want to KNOW why/what.
>>> >      
>>> > Why should the <video driver> go from good after boot, to bad after
>>> > the system is left unattended?  And that <disable/prevent the
>>> > sleep-mode> avoids the problem?
>>> 
>>> A bug in the video driver code, related to how the driver enables
>>> dpms[1] turn off/turn on, for your specific revision of the video
>>> chip. There is likely some register value that your chip revision
>>> needs set a certian way, and the driver simply is not setting it the
>>> right way.
>>> 
>>> Determining any more of a "why" than the above will require you to:
>>> 
>>>   1) start digging into the C code for the video driver for your chip;
>>>   2) have available to detailed programming specs. from the
>>>      manufacturer for your specific model/revision, including all
>>>      erratta.
>>>   3) hope that the documentation is complete and accurate
>>> 
>>> > It's been running for 3 days beeootifully.
>>> 
>>> > Is the video-driver inside the
>>> >  4940304 2009-08-17 07:53 vmlinuz-huge-smp-2.6.29.6-smp
>>> > or in the case of the few-months OLDER version which does NOT have
>>> > the problem, inside the <initrd.gz>
>>> 
>>> Part of the compiled binary of the driver is in one or the other.  the
>>> remainder is within the X server driver.  The compiled binaries will
>>> do you no good if you truly want to know "why".  You'll have to dig
>>> into the C code for the answer to that question.
>>> 
>>> 
>>> [1] I point at dpms here because dpms is the mode that requires
>>> programming the chipset to do something special.  There's a bug there
>>> somewhere from the sounds of things.
>> 
>> Remember the other quirk: that their's no problem, when a CRT is
>> plugged instead of the new LED:1920x1080.
>> --
>> My Windows-using mate insists that the vga is bidirectional; ie. that
>> the display informs the PC <what settings it needs>. Since the modern
>> LED:1920x1080 is forced to comply with the OLD vga spec. [and pin-out},
>> I don't believe him.
>> 
> Try looking up EDID. From wikipedia:
> The EDID includes manufacturer name and serial number, product type,
> phosphor or filter type, timings supported by the display, display size,
> luminance data and (for digital displays only) pixel mapping data.
> 
> Note the luminance data. It could poossibly be your display
> mis-informing the video card or its driver about its requirements.
> 
> You assume that the video card and driver behave exactly the same with
> the CRT and the LCD displays.
---
Yes, I don't believe that any signal goes from the display to the PC's
vga connector. Ie. it's NOT bidirectional.
Why else would the human need to tell the system about the displays 
parameters?

I looked at the EDID wiki, and don't like it;
although I can read/write schematic diagrams and design hardware.
The explanations [wiki] must be structured: like top-down-software.