Edid: What It Is And How It Works - Clarity SN-4610-1080 User Manual

3.3 Manual Selection and Adjustments
3.3.1 Selecting the Picture

3.3.1.2 EDID: What It Is and How It Works

EDID is the name of a method computers use to determine the characteristics of the computer moni-
tor.
EDID stands for Extended Display Identification
Data. It is the system behind Plug and Play. But just
knowing its name doesn't tell you how it works.
EDID is a block of 128 bytes of data residing in a
monitor that contains information about ...
• the manufacturer,
• the product ID,
• whether the monitor is analog or digital,
• video timings [resolutions],
• and color capability.
How EDID works
When a computer with EDID capability boots up,
it reads the EDID data in the monitor it is connected
to. It stores this data in the Registry (in Windows™)
where it is available to the video card.
Different video cards use this information in dif-
ferent ways. Many video cards will not send video
with resolutions that are not listed in the monitor's
EDID.
This dialog shows a setting of 1152×872 for the
1st monitor. If the #1 monitor were not capable of
this resolution, some video cards would not show
1152×872 in the dialog box.
EDID too small for Clarity displays
One problem with this system is that Clarity dis-
plays are capable of many more resolutions (video
34
timings) than can be store in a data block of only 128
bytes. Clarity displays are capable of hundreds of res-
olutions, but the EDID block has room to store only
dozens.
This means that some video cards will not put out
certain resolutions, even though the connected Clar-
ity display is capable of handling them. If the resolu-
tion you want to use is not listed in the Clarity
EDID, and the video card won't list that resolution
unless it is seen in the EDID, what can you do?
A possible solution is to uncheck the Plug and Play
box in the Miscellaneous menu (shown below). This
causes the EDID to use an incorrect CRC checksum.
Some video cards will see the incorrect checksum,
assume the data is corrupted, and fall back on a
default set of timings, which may include the one you
want.
Other cards may not bother to look at the check-
sum and limit the resolutions to those in the dis-
play's EDID.
Analog or digital
EDID works in either analog or digital mode, but
the Bay Cat must know which to use. You do this in
the Miscellaneous menu.
When EDID doesn't work
• There is no point in changing the refresh rate in
the Display > Settings tab > Advanced menu.
The Clarity display has a fixed refresh rate of 60
Hz. It will handle other refresh rates, but the
native refresh rate it fixed. The electronics system