From mboxrd@z Thu Jan 1 00:00:00 1970 From: Martin Steigerwald Subject: Re: 3.16, i915: less colors in X? Date: Sun, 22 Jun 2014 12:02:57 +0200 Message-ID: <5806451.MC4lLbjRSo@merkaba> References: <7569_1403385738_53A5F78A_7569_14810_1_2527490.06bevSLs0l@merkaba> <53A60C8B.3090106@rus.uni-stuttgart.de> Mime-Version: 1.0 Content-Type: text/plain; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable Return-path: Received: from mail.lichtvoll.de (mondschein.lichtvoll.de [194.150.191.11]) by gabe.freedesktop.org (Postfix) with ESMTP id EC28D6E292 for ; Sun, 22 Jun 2014 03:03:00 -0700 (PDT) In-Reply-To: <53A60C8B.3090106@rus.uni-stuttgart.de> List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: intel-gfx-bounces@lists.freedesktop.org Sender: "Intel-gfx" To: Thomas Richter Cc: intel-gfx@lists.freedesktop.org List-Id: intel-gfx@lists.freedesktop.org Am Sonntag, 22. Juni 2014, 00:51:55 schrieb Thomas Richter: > Hi Martin, Hi Thomas, > >> I'm trying to figure out how to ask X what color depth it is using...? > > = > > I think: > > = > > martin@merkaba:~> xdpyinfo | grep -i "depth of root" > > = > > depth of root window: 24 planes > > = > > but am not completely sure. > > = > >> This is thinkpad x60 with Debian 6.0.9. > = > AFAIK the 830GM chipset does not offer any support for hardware > dithering. Whether the panel in the x60 does I do not know, though. > = > However, what is remarkable is that graphics on a 16 bit(!) screen may > look more pleasing than graphics on a 24 bit screen, at least for such > ancient machines. The reason is that the panel cuts the bitdepth down > from 8 to 6 bits, without any dithering, just by cutting off the LSBs. > However, if you select a 16bpp mode to begin with, some desktop > environments (specifically gnome) apply a dithering of their own, even > though the output is only 5 bit per component. > = > This is at least what I see here on the IBM R31 and the Fujitsu S6010: > Gnome desktop at 16bpp looks better than the desktop at 8bpp, due to the > lack of hardware dithering. > = > The X11 intel driver had an option "Dac6Bit" to signal the 6 bit panel > resolution to X (even though the display pipeline operates in 8 bit > mode), but I have never seen this working in the past time. It seems not > to be supported anymore. Probably that's the culprit. > = > Martin, you should probably test Ville's alm_fixes5 kernel branch, its > support for the 830GM chipset of the X30 is in my experience much better > than that of the drm-intel-nightly or official kernels. I didn=B4t report this. I just mentioned how to find out the screen depth. = Pavel = reported this. On my ThinkPad T42 I do not compile own kernels anymore and = on = this ThinkPad T520 I will wait till 3.16-rc2. Thanks, -- = Martin 'Helios' Steigerwald - http://www.Lichtvoll.de GPG: 03B0 0D6C 0040 0710 4AFA B82F 991B EAAC A599 84C7