after 10.6.8 corrupted image on ext. display via DisplayPort

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after 10.6.8 corrupted image on ext. display via DisplayPort

my iMac 27 Mid 2010 (i7) with 1 Gb ATI 5770 video card has been working well with seccond monitor HP 2475w at 1920x1200 60Hz connected with mini DisplayPort - DisplayPort cable. After installing 10.6.8 I noticed corrupted fonts on the seccond dispaly. The image is being displayd the way as you would extend some low resolution into highres display however the sesolution itself is fine yet the image is mushed and soft especially it is clearly noticable with fonts being soft. After switching into DVI converter everything is well so at first I blamed the Displayport cable and ordered a new one. To my surprise the new Displayport cable does the same. I started to google and found few other threads on macrumors stating that 10.6.8 broke the displayport of macpro using 5770 card (same as in my iMac).

Can anyone confirm this being a 10.6.8 and this hardware/displayport cable related issue?

Is there any way to revert to 10.6.7 easily?

/Bartek

iMac, Mac OS X (10.6.8), iMac 27' Mid 2010 i7

Posted on Jul 1, 2011 2:49 AM

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Answer 1

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ba990300

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Jul 2, 2011 2:35 AM in response to Bartek72

Hi,

I am having the exact same Issue (iMac 27" i5 and HP LP2475w).

Using miniDP to DP ist not possible anymore with 10.6.8. The combination was working just fine with 10.6.7.

There is no solution yet but I think the technicians at apple know of the problem.

If they will resolve this? Who knows...

Probably just the apple-way to tell us not to buy different brands than apple.

/ba990300

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Answer 2

Bartek72 Author

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Jul 2, 2011 3:33 AM in response to ba990300

thanks for confirmation, I hope that Lion that is expected to be out this month is free from this bug and of course they should also fix it for SL eventhough the replacement hits the market.

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Answer 3

Jul 18, 2011 7:37 AM in response to Bartek72

I'm having the same issue with my 2011 iMac and HP LP2475w monitors. Everything just seems jagged, even more so when in the portrait position. Has anyone tried the developer preview of Lion yet...does it fix this issue?

And when you say "DVI converter", are you referring to the Apple mDP -> DVI connector?

Thanks!

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Answer 4

Bartek72 Author

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Jul 18, 2011 10:54 AM in response to ashleyjrw

I don't have the dev preview of Lion to test so wait for final one probably in few days from now. I hope that Lion dosn't have the same problem as now SL does after 10.6.8.

Yes I ment the mDP to DVI converter from Apple together with HP originally supplied DVI cable that came with my LP2475W. I have two of those HP monitors and both have the same issue with iMac after recent OS update.

DVI works fine however I had to color profile it again (new icc profile) as changing the cable/port changed the colors displayed on the HP.

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Answer 5

Jul 18, 2011 11:29 AM in response to Bartek72

Hopefully it does. I also have two of the monitors, and I don't particularly want to shell out £50/$80 for two converters…

Thanks!

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Answer 6

ba990300

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Jul 20, 2011 1:31 PM in response to Bartek72

No fix in Lion 10.7. !

So I guess we have to connect the HPs with a mDP to DVI-Adapter instead of a mDP to DP.

Although I would really like to know what they have changed from 10.6.7 to 10.6.8 and Lion.

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Answer 7

Bartek72 Author

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Jul 20, 2011 2:02 PM in response to ba990300

this is bad news than. I think that something with mDP support firmware must had been reworked as 10.6.8 introduced some "improvements" in thunderboldt support which goes via the same mDP ports on newer machines so probably newer port drivers broken the older mDP support.

I wonder if this is HP LP2475W issue only or any other DP enabled monitors have the same issue?

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Answer 8

ba990300

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Sep 2, 2011 9:59 PM in response to Bartek72

sorry, the problem still exists.

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Answer 9

Bartek72 Author

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Sep 3, 2011 6:28 AM in response to ba990300

Indeed, I tried it as well on 10.7.1 and it still displays corrupted image via mDP-DP cable while the mDP-DVI adapter and DVI cable works well since the day one of the problem occurrence in my case.

Today I also tried the mDP-HDMI cable and it worrk well as well yet I think DVI is probably a better solution then HDMI anyway.

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Answer 10

Sep 3, 2011 7:45 AM in response to Bartek72

I've fixed the issue with a non-Apple branded mDP -> DVI connector, using the DVI cable which came with the monitor. Only cost £10, versus £30 from Apple, and it works flawlessly.

http://www.amazon.co.uk/DisplayPort-Converter-Cablesson®-Unibody-MacBook/dp/B002 WP827E/ref=sr_1_2?ie=UTF8&qid=1315060931&sr=8-2

Thinking back, I did have the problem prior to 10.6.8 unlike some here, so maybe we have different display firmware or something. But regardless, I'm 99% sure this is a problem with the monitor. I've seen several reports of HP monitors having a poor DisplayPort implementation.

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