Potential fix for DVI problems with Samsung 191T's


V Green

NOTE: Long post. Get a Coke.

Well, I can hardly believe it, but I've got my Samsung 191T ver. 1 running
1280 x
1024 DVI off the 9600SE. It was a long and arduous trip - if you've been
the "no DVI on a flat panel but the analog VGA works OK problem", read on.I
hope this works for other folks, I'm gonna be really bummed if it doesn't-I
things that only work for me.

WARNING: Complex procedure only for the tech-savvy follows. If you don't
understand it, get your kids to help ;-) No guarantee of results
whatsoever - I
have only tried this on one 191T (mine). Since the DVI wasn't working
anyway, I
figured I couldn't screw it up any more, but that's always possible. DO

First some background:

I bought the 191T in Dec. 2002. At the time I was running a ECS-D6VAA mobo
and an ASUS 7700 GeForce2 analog only card. The 191T looked pretty damn
good on the VGA, and I decided to wait till my next mobo to upgrade to a DVI

That time came earlier this month, when I got an ASUS PC-DL dual Xeon MB (I
do LOTS of video transcoding). I bought a nVidia 5200 based card from
MadDog, as I've always had positive experiences with NV. Did a clean
install of
XP Pro to an empty HD at my office- I didn't have the Samsung there, just a
CRT, so I used the VGA connector.

Imagine the cursing and swearing when I brought the machine home, hooked it
to the DVI input of the 191, and saw..nothing. Nothing at all on power up,
POST, no device listing, although XP was going through all its startup
Anyway, used the old "tab-enter-tab-tab-enter" method to restart down from
(not visible) Welcome screen. Hooked up the VGA to the 191, restarted, and
had a desktop. Not a pretty one though, could never get the image quality
up to
that of my old 7700. But I could get work done, and that was important.

Soooo.time to google around and find out what the *)&%^$ is going on.

Searching on "DVI" + "problems" + "191T", unfortunately, returned a number
hits. I was not alone. This thread, in particular, pretty much covers it


(watch for URL wrap).

There's 50+ pages of people with problems here. Not a pretty picture.

But, it DID have some valuable information:

1. Going to a dual-link cable did NOT fix the problem.
2. Changing monitors (or even going to a newer ver. of the 191T) might fix
3. Jumping ship to ATI seemed to fix the problem.

I went with #3, and exchanged the 5200 for a 9600SE at Best Buy. I don't
I use the workstation for work. Right away, things were different: POST
device listings would show on the DVI cable, where previously they did not.
blank screen at the XP Welcome screen, just as many of you have. VGA was
OK, and image is MUCH superior to VGA on the nVidia card.

The above link had a couple posts from "shg" that were fairly glossed over
by the
rest of the participants, but seemed rather significant to me, as I'm a
nut from way back. Apparently, the EDID from the DVI side of the 191T
translates to some old 15" analog-only monitor that Samsung made (the
530/531T), NOT the 1280x1024 191T. This sorta made sense, as I could load
up a 1024 x 768 desktop in Safe Mode using the built-in XP driver. Dog slow
though-no driver optimizations.

So, I reasoned that what was happening here was:

During POST and startup, the 9600SE had negotiated just enough protocols via
DDC2 on the DVI port to run these screens at 1024 x 768, but when the Cats
took over, they examined the EDID info for the DVI port and called bullsh*t
on it,
as it's kinda a mess, and switched back to the VGA port, which output a
EDID. When checking the monitor connected to the DVI port when at the VGA
desktop, I could see my old friend the 530/531T listed there as connected to

In the Dell thread, a couple users said that they got their LCD's to work by
9800's. OK, I'm made of money (right, but I really wanted this to work), so
off to
BestBuy. Long story short, 9800PRO/128 same as the 9600. POST, etc, but no
desktop. Fiddle with it for a few days, exchange it for NV 5900 XT as other
info I
gathered during my quest suggested that some users got THIS card to work.
dice. Back to the old NV problem-no POST, no nothing. XP loads OK as
evidenced by desktop sounds. VGA works. Well, at least they act different
ATI cards. Perhaps that's relevant.

OK, time for some tools:


scroll down to near the bottom and look for the EDID.EXE app. This will
you to see the EDID of the monitor hooked to the VGA port (wouldn't do the
AND, as you tab through the 128 different values for the EDID, explains them
you. As does this .PDF from VESA:


Especially interesting to me was the EDID value at 20H, the definition of
is on page 18. "Digital displays must set bit 7 of the video input
(offset 14h) equal to one. Bits 6-1 must be set to 0." Cool. Now, I just
needed a
util that would read/write the EDID of the broken DVI port of the 191T.

Spent a LOT of time on this one, for some weird reason, the EDID structure
some kinda damn VESA secret that they want you to pay for. Turns out that
the DVI_RECOVER utility that Dell is e-mailing to folks with broken FP
will do it (mentioned in the Dell link).

Get it here:


Instructions on how to use it here:


(url wrap again)

Now for the kicker:

The damn utility did NOT work with my 9600. Couldn't read the EDID at
all-errors out. BUT, it
DID work when I put the 5900 back in! The whole thing runs from a DOS 6.2
floppy. There's also
an option to create a ISO bootable image if you don't have a floppy. Be
VERY sure, after you
create the diskette/CDR, that you rename AUTOEXEC.BAT before booting with it
or it'll autorun
some stuff to try to read/restore the EDID's without your supervision. I
never let it do this. If you
find out that you can't read EDID's through your ATI card as well, borrow
somebody's NV card.
You'll need one that has a DVI port. I would REALLY like to know if anyone
gets this to work with
an ATI card.

To see how the main .EXE (DDCW) works, just type DDCW at the command prompt
after the
floppy has booted to the A:> prompt.

To see the EDID for the VGA port:

DDCW -m 0

To see the EDID for the DVI port:

DDCW -m 1

Try JUST these first, to make SURE you can see them both. If you can't, I
really don't know
where to go, they just worked for me.

To save the results of the above so you can boot back into XP and look at
and manipulate them,
just do this:


These commands send the same stuff you displayed earlier to two files named
and DVIPORT.TXT. You'll need them later.

Anyway, sure enough, upon examining the output from the utility, the value
at 20H for the DVI
port on the 191 was that of an analog monitor (you can find out using the
ViewSonic utility-read
on).no wonder the sumbitch wouldn't run digital. Stupid Samsung.

You don't need to do the following unless you want to confirm that your
value at 20h is bad, but
the procedure will be the same for the final solution, so read it through.

Start a "New" EDID grid in the ViewSonic utility by using File>>New. Then
enter the values you
got from DDCW into the boxes. I know, tedious and no fun, but neither is
screwing over your
monitor if you don't get it right. Save the whole mess (File>>Save) with a
..DAT extension so you
can get at it again. Then, click your way through the values from the start
until you get to the first
one on the left, third row down (next to the 20). The always helpful
explanation box on the right of
the EDID grid calls this out as "Video Input Defination" (their spelling
error). If you then click the
"Modify EDID" button at the top to turn it ON, and then click the radio
button that says "Digital",
the editor will calculate the value that belongs here-for the record my
original value was 0Fh, and
the Editor says it should be 80h for digital. I didn't select the "DFP 1.x
compatible" option. You
will also notice the last value in the grid change-this is an automatically
calculated checksum for
the EDID string. Save your modded EDID under a different name as described
above. NOTE:
don't "Export Binary EDID file" - you can't use it.

This modded EDID is STILL not usable at this point, but in my
experimentation, I wanted to try it.
So, I edited the "bad" EDID string I saved earlier (DVIPORT.TXT) to reflect
the changes I made to
the value at 20h (new value = 80h) AND the last value (the checksum) to
whatever it got changed
to (this will vary from monitor to monitor). Use Notepad to edit. Also
trim off the extra crap from
the beginning and the end. The "raw" output from DDCW looks like this:

EDID update utility
use: -f <filename> to specify the text file containing the correct
EDID data for compare and reprogram
use: -c <filename> to specify the text file containing the correct
EDID data for compare ONLY
use: -p to automatically update the first 8 bytes of the A0 EDID to 00 FF FF
use: -m A to specify the output to use, A=0 (default) for VGA, A=1 for DVI
use: -q to suppress most output
-f -c and -p are mutually exclusive options: use only one of these

EDID read from device:
00 FF FF FF FF FF FF 00 10 AC 03 A0 4C 45 30 30 1D 0D 01 03 80 29 1F 96 EA
4C 40 A1 57
4C 97 26 1C 50 54 A5 4B 00 81 80 A9 40 71 4F 01 01 01 01 01 01 01 01 01 01
48 3F 40 30 62
B0 32 40 40 C0 13 00 6F 13 11 00 00 1E 00 00 00 FF 00 39 45 32 34 39 33 37
49 30 30 45 4C
30 00 00 00 FC 00 44 45 4C 4C 20 32 30 30 30 46 50 0A 20 00 00 00 FD 00 38
4C 1F 50 10 00
0A 20 20 20 20 20 20 00 97

(don't use ANY of this stuff, this is just an example).

You need to trim off all the stuff from the beginning AND any trailing
spaces after the EDID so
you're left with this:

00 FF FF FF FF FF FF 00 10 AC 03 A0 4C 45 30 30 1D 0D 01 03 80 29 1F 96 EA
4C 40 A1 57
4C 97 26 1C 50 54 A5 4B 00 81 80 A9 40 71 4F 01 01 01 01 01 01 01 01 01 01
48 3F 40 30 62
B0 32 40 40 C0 13 00 6F 13 11 00 00 1E 00 00 00 FF 00 39 45 32 34 39 33 37
49 30 30 45 4C
30 00 00 00 FC 00 44 45 4C 4C 20 32 30 30 30 46 50 0A 20 00 00 00 FD 00 38
4C 1F 50 10 00
0A 20 20 20 20 20 20 00 97

Turn off Word Wrap in Notepad so it's just one long line you have to scroll
back and forth to see.
Make DOUBLE SURE there's NO spaces BEFORE or AFTER this string. I don't
know if DDCW
automatically strips them when it writes to your monitor, so I wasn't gonna
take any chances.
Save the EDID with whatever name you want as long as it's different from the
original (you'll need
that later). The make sure to save it to the floppy where DDCW lives as
well, you'll be doing all
your work from there.

To upload your new EDID AFTER triple checking everything (I have no idea
what will happen if
you upload a bum EDID to your monitor, and I don't wanna find out), boot the
DDCW floppy

Then enter:


Where FILENAME is your modded EDID.

DDCW will first READ the current EDID, then DISPLAY your modded one. Then,
it goes dormant
for awhile-just wait. It'll return (hopefully) with a success message.

Anyhooo, after I uploaded this modded semi-final EDID, the 5900 card, which
would NOT display
ANYTHING before, would now show POST! WooHoo!!! I'm on the right track!
Apparently, NV
cards are more picky about whether or not the monitor is flagged as being
digital capable during
POST than ATI cards are.

Put the 9600SE back, still couldn't boot to the desktop in DVI, but nothing'
s broken either. Time
for the next step-taking the EDID from the ANALOG side of your LCD, modding
it so it makes the
DIGITAL side of your monitor look the part, and uploading it to the panel.

You will need the monitor driver .INF file for the digital side of your LCD
to finish this. For the
Samsung, I just downloaded it. If you look at the .INF file for your
monitor, you should see an
entry for the ANALOG side and an entry for the DIGITAL side. For the 191T,
the analog side is
identified as SAM0013 and the DIGITAL side as SAM0014. As part of the
screwed up digital
EDID, my 191 digital side was being id'd as a SAM6056 (the damn 530/531T).
This is the other
thing you gotta change to get the digital side EDID to work if yours isn't
right. Open up Notepad
twice and load your VGA and DVI EDID's you got with DDCW. Here's mine
(before modding):

DVI port:

EDID read from device:
00 FF FF FF FF FF FF 00 4C 2D 56 60 00 00 00 00 2E 0C 01 01 0F 1E 17 61 E8
B5 A5 9E 57
4C 98 25 1A 4B 53 B7 6E 00 31 4F 45 4F 61 4F 01 01 01 01 01 01 01 01 01 01
4E 0C 80 C8 20
E0 14 10 10 40 13 00 30 E4 10 00 00 18 56 13 20 00 31 58 19 20 10 50 13 00
30 E4 10 00 00
1E C3 1E 00 20 41 00 20 30 10 60 13 00 30 E4 10 00 00 1E 00 00 00 FD 00 32
4B 1E 3D 08 00
0A 20 20 20 20 20 20 00 A8

VGA port:

EDID read from device:
00 FF FF FF FF FF FF 00 4C 2D 13 00 39 31 48 47 2F 0C 01 03 0F 26 1F 8C EA
6F 8B A2 5A
4D 94 24 1A 51 56 BF EF 80 81 80 61 40 45 40 31 40 01 01 01 01 01 01 01 01
30 2A 00 98 51
00 2A 40 30 70 13 00 78 2D 11 00 00 1E 00 00 00 FD 00 38 55 1E 51 0D 00 0A
20 20 20 20 20
20 00 00 00 FC 00 53 79 6E 63 4D 61 73 74 65 72 0A 20 20 00 00 00 FF 00 48
43 46 54 42 30
32 39 39 30 0A 20 20 00 E7

The SAM0013 and SAM0656 strings are contained in the 10 bytes starting at
the 9 th group of
double digits from the beginning. In my case you can see the 0656 and the
0013 in reverse order
at group 11 and 12 (computerese-you programmers are used to this). Since
the SAM was
common to both ID's all I needed to change was the 13 00 on the VGA port
EDID to 14 00. This
would now ID the monitor as SAM0014, which, according to the Samsung .INF,
is what the digital

There are two other changes you'll need to make as already mentioned-you
need to change the
capabilities of the monitor to DIGITAL and enter a new checksum value.
Easy-just use the
ViewSonic utility. Retrieve the VGA EDID with it. Verify it's the right
one-I couldn't see the DVI
EDID at all if I didn't have it hooked up. Change the values as described
above-your monitor ID
string may be different. Enter the 80h at the proper spot (next to the
20-see above) The
checksum (last box in the grid) will change as you change values. Save as
whatever.DAT again.

Keep the ViewSonic util open and then open your ANALOG EDID in Notepad so
you can see
them both. VERY CAREFULLY compare the EDID values in each, and change the
ones in
Notepad to the values in the ViewSonic app. Double check everything, make
sure there's no
spaces b4 or after in the stuff in Notepad, turn off word wrap, etc, and
save with another
filename.txt. Then copy this <final> EDID to your DDCW floppy and reboot
with it.

After you're booted from the floppy, do this:


Where FILENAME is your final modded EDID.

Same stuff should go on as described above.

To test if it took, do:

DDCW -m 1

Examine the result, look for your changes. Power down, boot from the floppy
again, check with
DDCW again to see if it stuck. I have heard of some LCD's not having
programmable EPROMS
containing the EDID (not writeable), if you have one of these, I don't know
what's gonna happen.
I would hope DDCW would barf an error when you try to upload.

Take out the floppy, put your original vid card in, reboot with the VGA
cable to the XP desktop, to
make sure you can still get in. Then, power down, disconnect the VGA cable,
reconnect the DVI
cable, boot up and hold your breath.

Hot damn, digital via DVI looks friggin good! Well worth the (many) hours I
spent jacking around
with this.

If your screen is still blank, you can restart from the Welcome screen by
pressing "tab-enter-tab-
tab-enter" and yanking off the DVI cable so it'll use the VGA port. All I
can suggest at this point is
to carefully re-check your work.

If you have a 191T, and you're having the problems I had, here's the modded
EDID I used-if you
feel brave, read through the entire procedure to make sure you understand
what's going on, cut &
paste this into Notepad, make sure there's no leading/trailing spaces, turn
off word wrap and
backspace it all into one big long line and save. Then use DDCW as
described to upload it.

00 FF FF FF FF FF FF 00 4C 2D 14 00 39 31 48 47 2F 0C 01 03 80 26 1F 8C EA
6F 8B A2 5A
4D 94 24 1A 51 56 BF EF 80 81 80 61 40 45 40 31 40 01 01 01 01 01 01 01 01
30 2A 00 98 51
00 2A 40 30 70 13 00 78 2D 11 00 00 1E 00 00 00 FD 00 38 55 1E 51 0D 00 0A
20 20 20 20 20
20 00 00 00 FC 00 53 79 6E 63 4D 61 73 74 65 72 0A 20 20 00 00 00 FF 00 48
43 46 54 42 30
32 39 39 30 0A 20 20 00 75


I didn't uninstall the ATI vid card drivers or otherwise touch my XP Pro
install during this stuff. If
you have to temporarily use a nVidia card, it won't matter, as all the stuff
you're gonna do with it is
in DOS. I just put my ATI card back in when I needed to use XP to edit EDID
's and stuff, then put
the NV card back when I uploaded to the monitor.

I know this is a REALLY complex procedure. I am in NO WAY recommending it
to beginners. I
have NO IDEA how it'll work on other LCD's as I only have the one ;-) but
the underlying
principles seem to be usable for others. The info in the VESA spec document
is pretty clear that
all manufacturers should be following it.

To their credit, the ATI techs have been working with me on this for a few
weeks now. We had
been assuming it was a driver issue though. I'll let them know if a few
people other than myself
get it to work-then we know it's not a fluke.

If I can, I'll clear up any questions, just leave them in the thread so all
can benefit. Sometimes I
don't check in here every day.I'll be back.

My motivation - I love messing with hardware and learning things and my eyes
are getting old and
need the sharpest display I can get (lotsa CAD work), and I paid good $$$
for a DVI capable
monitor and the whole thing just pissed me off.


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