Max PixClock 250MHz... why?

H

HenkK

Junior Member
I'm considering switching from VMware Fusion to Parallels 7 on my 27-inch iMac.

I've installed Debian GNU/Linux "testing" with 3.0 kernel (amd64) in a Parallels 7 VM, for which Parallels Tools installed just fine. The problem I have is with the screen resolution: there is just no way of getting an acceptable ModeLine for "2560x1440" at 60Hz, since the maximum Pixel Clock for the Parallels virtual graphics device seems to be limited to 250MHz (my desired ModeLine requires 311.83).

When I specify the "2560x1440" mode in my xorg.conf, then (at the end of Xorg.log) a "PRLCONTROL" driver effectuates a "dynamic" switch to 2560x1440, but this causes problems when opening my Gnome desktop: there is some "sectioning" of the screen taking place (apparently when switching from 1920x1200 to 2560x1440), that messes with the location of icons in the the top and lower menu bars, and that also prevents my font size preferences to be applied properly. This is a miss-and-hit phenomenon, it may or may not disappear after logging out and logging back in as user.

FWIW, in a similar installation with VMware Fusion the VMware "legacy" video driver allows a maximum Pixel Clock of 400MHz, and in that case Xorg just accepts my ModeLine for 2560x1440@60Hz just fine.

Is there a way of increasing the maximum Pixel Clock on the PRLVIDEO driver?
 
Henk,

Thanks for pointing that out. 250MHz is indeed the maximum pixel clock allowed for standard EDID. I filed bug internally to remove the limitation.
 
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@serv What is the status of this matter? Has the max Pixclock been increased since I first posted on this issue in September 2011?
This is somewhat important to me, as I have a currently unused license for Parallels 7...
 
serv said:
Large resolution should work in 7.0.15094
Click to expand...

...except, it still doesn't. Looking at Xorg.log.0 shows that the PixelClock for the Parallels vesa driver is still
limited to 250 MHz. My 27-inch iMac display needs the following Xorg modeline

311.83 2560 2744 3024 3488 1440 1441 1444 1490 -HSync +VSync

in order to run at 2560x1440 @ 60Hz. As you can see, this requires a PixelClock of 311.83 MHz...

Right now, I can use that beautiful display in Parallels only at 1920x1200 resolution, which just isn't good enough.
Why can't Parallels Desktop for Mac do what VMware Fusion have done for years (i.e. use 400 MHz as maximum
PixelClock)?
 
Have you updated Parallels tools to 15094 too?
For starters, virtual display has no maximum frequency per se. As of now Parallels virtual display EDID reports 2.5Ghz px clock, and that's Xorg code that clamps it to 250Mhz. Parallels Xorg module _does_not_ filter out modes by pixel clock, can set almost anything that fits in memory.
You don't have to configure old-fashioned display mode lines in Parallels, these might indeed be subject to filtering by Xorg. What you need is to choose desired mode in Parallels Screen section, all of your native display resolutions are already listed by the driver.
If that still doesn't work, post you Xorg.log here.
 
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@serv Yes, I did update the Parallels Tools as well, and it installs OK in amd64 Debian testing (Wheezy).
But now there's another problem: Xorg never starts up properly, only showing a black screen. Rebooting
in recovery mode and trying to check /var/log/Xorg.0.log shows there to be dozens of Xorg.xxx.log(.old)
files around, all with the same time stamp, most of these very short and ending in the error message
"xf86OpenConsole: Cannot find a free VT". This seems to point to a problem with the "prlvideo" driver in
Parallels Tools.

Parallels will probably say that they don't support cutting edge Linux distributions right-away, but this
underscores my request for an increased PixelClock of the Parallels virtual graphics card. Many users,
certainly myself, are running cutting edge distributions in VMs, and don't want to wait for Parallels Tools
to catch up (if ever). It is then necessary for users to be able to provide a suitable resolution/ModeLine
themselves -- 2560x1440@60Hz is not even a very exotic resolution, as it is that of a regular 27-inch iMac.

So, I'm asking again: why can't Parallels upgrade that PixelClock?
 
serv said:
... You don't have to configure old-fashioned display mode lines in Parallels, these might indeed be subject to filtering by Xorg.
Click to expand...
I don't see how this can be right, certainly Xorg does not filter, or clamp down, an identical installation in a VMware Fusion VM (with max PixelClock set at 255 MHz). Anyway, see my other post for reasons why Parallels should upgrade de max PixelClock in its virtual graphics card.
 
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