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Potential fix for DVI problems with Samsung 191T's
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 having 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 hate 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 THIS STUFF AT YOUR OWN RISK!! 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 card. 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, no POST, no device listing, although XP was going through all its startup noises. Anyway, used the old "tab-enter-tab-tab-enter" method to restart down from the (not visible) Welcome screen. Hooked up the VGA to the 191, restarted, and I 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 of hits. I was not alone. This thread, in particular, pretty much covers it all: http://forums.us.dell.com/supportfor...monitor&messag e.id=27226&view=by_date_ascending&page=1 (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 the problem 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 game, I use the workstation for work. Right away, things were different: POST and device listings would show on the DVI cable, where previously they did not. But, 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 hardware 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 valid 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 it. Crap. In the Dell thread, a couple users said that they got their LCD's to work by getting 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. No 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 than ATI cards. Perhaps that's relevant. OK, time for some tools: http://www.viewsonic.com/support/drivers2.htm scroll down to near the bottom and look for the EDID.EXE app. This will allow you to see the EDID of the monitor hooked to the VGA port (wouldn't do the DVI) AND, as you tab through the 128 different values for the EDID, explains them for you. As does this .PDF from VESA: http://www.vesa.org/public/EEDIDguideV1.pdf Especially interesting to me was the EDID value at 20H, the definition of which is on page 18. "Digital displays must set bit 7 of the video input definition (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 is 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 displays will do it (mentioned in the Dell link). Get it he http://www.jeffgeiger.com/stuff/dvi_recover.htm Instructions on how to use it he http://forums.us.dell.com/supportfor...message.id=337 21 (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: DDCW -m 0 VGAPORT.TXT DDCW -m 1 DVIPORT.TXT These commands send the same stuff you displayed earlier to two files named VGAPORT.TXT 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 FileNew. 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 (FileSave) 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 FF FF FF FF 00 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 again. Then enter: DDCW -m 1 -f FILENAME.TXT 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 side SHOULD HAVE BEEN ALL ALONG! 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: DDCW -m 1 -f FILENAME.TXT 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 NOTES: 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 ****ed me off. |
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