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Author Topic: Moninfo & Windows 7 - EDID from registry missing 2nd block  (Read 12954 times)
SantzHex

Posts: 1


« on: January 22, 2010, 11:14:03 AM »

I've been testing out Windows 7 on many PCs, laptops, etc. and have noticed that the 2nd EDID block is not recorded into the Windows 7 registry.  Connect any HDMI display as the sink, and everything works correctly, but only the first 128 Bytes of EDID are recorded in the registry. 

Using Moninfo, the "Real Time" entry shows all 256-Bytes of data correctly, however the "Registry" entry for the same Display ID only shows 128-Bytes, with the extension bloc flag listed as "Reserved - 0x00".  I verified that the EDID is only 128 Bytes in the registry as well.  With Windows XP this does not occur - all 256 Bytes are listed in the registry (for the same system & display combo).

Has anyone else noticed this?  Is it possible that this is an intended change or a bug in Windows 7?   Maybe the extension block data is now stored elsewhere?  At any, rate this is not a "problem" really, just a general query.
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ernesto

Posts: 32


« Reply #1 on: February 02, 2010, 10:10:30 AM »

Same problem here.
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hiroo

Posts: 1


« Reply #2 on: February 03, 2011, 12:46:42 AM »

me too.
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Ashley Saldanha
Administrator
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Posts: 1806


« Reply #3 on: February 03, 2011, 03:18:29 AM »

I don't work for Microsoft, but since the question is posted here, I'll hazard an answer. I think the difference is that Microsoft previously supported old P&D type 256-byte EDIDs (EDID 2.0), a stillborn standard that was cancelled a long time ago by VESA and never used by the CEA. In other words, Windows has always used and recorded only the *first* data bloc. Its just that under Win2k/XP xpdm drivers the first data bloc could be 256 bytes, so if the 256 bytes happened to contain a CEA extension bloc rather than a 256 byte base block, you found that in the registry. P&D monitors with 256-byte base EDIDs aren't supported by Vista/Win7 wddm drivers.

When monitors are enumerated by the display driver, only the first data bloc is read and stored in the registry. Extensions blocs are read as needed, so there is no real problem/bug/error here.

As for why MonInfo shows the extension bloc as "Reserved" when decoding the registry data, that's simple: the base EDID only shows how many extension blocs there are, not the type. You have to examine the actual extension block data itself to see what type of data it contains, and since that data isn't in the registry, it is tagged by MonInfo as reserved.

 
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