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<th>Bug ID</th>
<td><a class="bz_bug_link
bz_status_NEW "
title="NEW - radeon: allow the user to set a maximum HDMI pixel clock (in MHz) by a kernel parameter"
href="https://bugs.freedesktop.org/show_bug.cgi?id=93885">93885</a>
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<th>Summary</th>
<td>radeon: allow the user to set a maximum HDMI pixel clock (in MHz) by a kernel parameter
</td>
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<th>Product</th>
<td>xorg
</td>
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<th>Version</th>
<td>7.6 (2010.12)
</td>
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<th>Hardware</th>
<td>Other
</td>
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<th>OS</th>
<td>All
</td>
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<th>Status</th>
<td>NEW
</td>
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<th>Severity</th>
<td>normal
</td>
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<th>Priority</th>
<td>medium
</td>
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<th>Component</th>
<td>Driver/Radeon
</td>
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<th>Assignee</th>
<td>xorg-driver-ati@lists.x.org
</td>
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<th>Reporter</th>
<td>estellnb@elstel.org
</td>
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<th>QA Contact</th>
<td>xorg-team@lists.x.org
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<div>
<pre>As far as I have seen radeon sets the pixel clock (in MHz) for the HDMI/DVI
output to a value as recommended by the firmware, only. Since kernel 4.5.0 the
nouveau driver has a kernel parameter called hdmimhz to override this setting
by hand: As far as I could test it the results I get that way are just
wonderful (see for <a class="bz_bug_link
bz_status_NEW "
title="NEW - nouveau: Xorg crashes sooner or later in 3840x2160 mode"
href="show_bug.cgi?id=93405">Bug 93405</a>).
The situation with my '4K ready' XFX Radeon R5 230 card is similar than it
was with the nouveau driver before kernel 4.5.0: The promised 3840x2160@30 mode
is not offered by default and when I try to set this mode manually the screen
remains black (no signal). It was exactly like this with my Nv. Geforce 9600M
GT until the hdmimhz kernel parameter appeared. Since then it works even better
than officially specified by Nvidia with nouveau (nobody would have believed
that).
Why isn`t there a similar parameter for radeon?
kernel version: 4.5.0-rc1-ARCH #2 SMP PREEMPT
radeon driver (xf86-video-ati/arch): 1:7.6.1-1</pre>
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