Gefen DVI DL: Dual Link DVI + USB KVM
by Anand Lal Shimpi on October 19, 2005 12:05 AM EST- Posted in
- GPUs
Once More, with a DVI Detective
As we mentioned before, Gefen's DVI Detective is a programmable box that will record your monitors EDID information and, once recorded, will continually transmit it to the host machine to trick it into thinking that the monitor is still present.
Luckily, the DVI Detectives solved our OS X problem - now OS X stopped thinking that the monitor was unplugged every time that we switched away from the G5, and we stopped getting screen corruption upon the switch back. Also, with the presence of a DVI Detective on both machines, you no longer have to switch to the machine before starting it up. You can boot both machines without switching to either one, and still have full access as soon as you switch over.
The DVI Detectives also fixed the Cinema Display's USB hub problem. Now we could plug the hub into the DVI DL and switch between systems without losing keyboard/mouse support when switching back to OS X.
Unfortunately, our problems weren't over.
The inclusion of the DVI Detectives meant that we had one extra DVI cable per computer. In other words, the length that the DVI signals had to travel had just gone up by one more cable length. This translated into noticeable visual artifacts on the screen, individual pixels, or often times lines of pixels flickering would be the result.
Fine tuning the EQ knob would always get rid of the flickering, but what we found was that they would return depending on what we had on the screen at the time. The biggest culprit appeared to be playing a DVD. As soon as we'd start up a DVD, we would see many more flickering pixels than before. Part of it was due to the fact that the flickering pixels were more visible on black backgrounds, but once we adjusted the EQ knob to fix the issue on the DVD playback screen, it would return as soon as we stopped playing a DVD. The same applied to various other tasks that we performed on the computer, mostly involving the use of different colors than with what we adjusted the EQ knob originally. The end result was that we could never obtain an artifact-free picture with the DVI DL.
Naturally, we asked Gefen about the problem, and once more, Gefen was very quick to respond - although we weren't happy with their response. Apparently, this is a known problem with the DVI DL, and the engineers at Gefen are working on an auto-EQ that will constantly vary the EQ knob settings in order to fix this problem in all environments. Unfortunately, there is no ETA on the fix, nor is it known whether or not the fix can be retrofitted to current DVI DL units. Should the fix only require a firmware update, Gefen will add the fix to current DVI DL units under warranty. If it is a more substantial upgrade, however, current DVI DL users will have to simply purchase a new unit. To their credit, Gefen offered to refund our money after we asked them about the issue.
As we mentioned before, Gefen's DVI Detective is a programmable box that will record your monitors EDID information and, once recorded, will continually transmit it to the host machine to trick it into thinking that the monitor is still present.
The DVI Detective has rubber feet to prevent it from sliding around your desk.
Luckily, the DVI Detectives solved our OS X problem - now OS X stopped thinking that the monitor was unplugged every time that we switched away from the G5, and we stopped getting screen corruption upon the switch back. Also, with the presence of a DVI Detective on both machines, you no longer have to switch to the machine before starting it up. You can boot both machines without switching to either one, and still have full access as soon as you switch over.
The DVI Detectives also fixed the Cinema Display's USB hub problem. Now we could plug the hub into the DVI DL and switch between systems without losing keyboard/mouse support when switching back to OS X.
Unfortunately, our problems weren't over.
The inclusion of the DVI Detectives meant that we had one extra DVI cable per computer. In other words, the length that the DVI signals had to travel had just gone up by one more cable length. This translated into noticeable visual artifacts on the screen, individual pixels, or often times lines of pixels flickering would be the result.
Fine tuning the EQ knob would always get rid of the flickering, but what we found was that they would return depending on what we had on the screen at the time. The biggest culprit appeared to be playing a DVD. As soon as we'd start up a DVD, we would see many more flickering pixels than before. Part of it was due to the fact that the flickering pixels were more visible on black backgrounds, but once we adjusted the EQ knob to fix the issue on the DVD playback screen, it would return as soon as we stopped playing a DVD. The same applied to various other tasks that we performed on the computer, mostly involving the use of different colors than with what we adjusted the EQ knob originally. The end result was that we could never obtain an artifact-free picture with the DVI DL.
Naturally, we asked Gefen about the problem, and once more, Gefen was very quick to respond - although we weren't happy with their response. Apparently, this is a known problem with the DVI DL, and the engineers at Gefen are working on an auto-EQ that will constantly vary the EQ knob settings in order to fix this problem in all environments. Unfortunately, there is no ETA on the fix, nor is it known whether or not the fix can be retrofitted to current DVI DL units. Should the fix only require a firmware update, Gefen will add the fix to current DVI DL units under warranty. If it is a more substantial upgrade, however, current DVI DL users will have to simply purchase a new unit. To their credit, Gefen offered to refund our money after we asked them about the issue.
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Tutor - Sunday, October 30, 2005 - link
Dr. Bott has great KVMs. I use a VGA with USB switcher and it is great. Did not have the opportunity to test their DVI product, but maybe Anand will ;-)It is not dual link, but rated for 1920 * 1200. German web site states a dual link device will be available in the future.
http://www.drbott.com/prod/db.lasso?cat=moniswitch">http://www.drbott.com/prod/db.lasso?cat=moniswitch
kencl - Monday, October 24, 2005 - link
Just thought I'd pass along http://www.kavoom.biz/">another software solution. It's M$ Windows only unfortunately, but that may be exactly what some of you are needing (not me, unfortunately, I need to switch into a Linux system - maybe there's an Win32 X-Windows client out there somewhere....)supaxi - Saturday, October 22, 2005 - link
I know this is a bit out of left field, but I wanted to mention a software KVM program that I use a lot. It lets you use one mouse and keyboard with any number of systems. I use three computers at work and this is real life saver as I hate KVM switches. You can try it at http://www.neslosoftware.com">http://www.neslosoftware.comThey don't support unix but I'm sure you could find a similar program out there someplace.
tortoisehead - Thursday, October 20, 2005 - link
I bought a gefen switcher a few weeks ago because remote logins don't cut it for video or gaming, and I was sick of switching the usb and dvi cables between my pc and mac. I have the "2x1 DVI KVM" and have had several issues like the ones the reviewers came across. In case there are other gefen owners reading this article, here's some info on how I got my setup to be stable.I went through hell just trying to to get the ability to switch back and forth between my PC and Mac without praying that it would work correctly. You wouldn't think a switcher would be that hard, but like others have said no one can seem to get it right. I had crashes, devices not being recognized correctly, and the monitor not turning on when I switched. Sometimes repeatable, sometimes not. That can be so frustrating.
In the end I replaced the DVI cable going to my Mac with one I got from work (from Dell). That ended the dock crashing every time I switched back to my Mac. Who knows what is wrong with the cable that gefen gave me. I asked in their forums, and they recommended to pull out one of the DVI pins! Too bad after I did that the cable didn't work at all anymore.
As far as the PC, I had two wireless logitech controllers that were apparently causing issues with the switcher and XP. One for the keyboard, and one for the mouse. Once I set it up to communicate with both devices using the keyboard controller, I removed the mouse-only controller and had no more usb problems.
One of the most frustrating things I ran into was the same thing documented in the review. You bring up any problems in the gefen forum and the first thing they tell you is to buy their $80 "DVI Detective" to fix their own buggy hardware! That's just lame, especially with the price of DVI switchers. And if Macs have problems with DVI cables having certain pins, why not have the option of one of your DVI cables being a "Mac" version when you buy the switcher?
So long story short, I can't really recommend gefen's products either. Please chime in if you have had a great experience with an affordable DVI switcher!
Scorpion - Thursday, October 20, 2005 - link
Wow I'm so happy to see a KVM article! I still use my old Hawking 4-Port KVM. I've been trying to upgrade to a newer KVM with DVI and USB support for mouse and keyboard, but I just can't find any! I was even at a Fry's (out of town, there isn't one where I live) and I looked at this huge Isle of KVMs, and I could maybe find ONE that supported DVI or USB, but never both, and the ones I found just didn't have the functional look I wanted. Where is this market? I know several people with multiple computers and limited desktop real-estate for multiple monitors, keyboards, and mice. KVMs are great for this situation, there just aren't enough people who do it right.I'm really looking for a good KVM DVI+USB, not to be used with any wireless keyboard or mouse. If anyone has any recommendations I'd greatly appreciate it. It's good to see some attention pointed towards this market segment.
Nocturnal - Wednesday, October 19, 2005 - link
I wonder if more sites did more reviews on KVMs that they'd kinda get to work on fixes for the flaws that the reviewers find. I want the IOGear GCS1774 but it does not work with any nVidia 3/4 chipset which is very bad.ky - Wednesday, October 19, 2005 - link
How do you get a 30" for $2500?Pixar and Apple employees get a standard discount of 15% before tax so that comes pretty close to $2500 ($2549). Maybe reviewers get > 15% off? Or another reason might be due to cash back discounts or site referrals (fatwallet) you might bring it closer to $2500.
Why buy a $400 switcher when a 2nd 20" display is only $400?
I dunno about you but if both my computers can power the 30" in all its magnificence, I'd rather use the 2nd computer w/ the 30" than a piddly 20". OTOH, w/ a 2nd monitor, you can use both at the same time rather than alternatively. It's just a preference thing, I guess.
Gefen has has a long history of "screwing" their customers with their suggestions (read: upselling) of buying additional products to solve problems with products you've already purchased. Back when I was using the 23" display, they suggested I buy a 2nd identical product to troubleshoot my existing ADC Switcher w/o any mention of sending one back or for credit. Even the CS rep remarked that I probably didn't want to do it but it was a suggestion. Don't hold your breath on the integration of Auto-EQ or DVI Detective into the next version of the DL KVM, they've said things in the past about previous products having problems and perhaps addressing them in a future version of the product but they never followed through.
n7 - Wednesday, October 19, 2005 - link
Remind me to never ever purchase a Gefen product.Any company that has the nerve to suggest i buy another product to make their own defective product work properly can go DIAF, to put it nicely, LOL.
Aquila76 - Wednesday, October 19, 2005 - link
Try finding a KVM (DVI or not) that works with a USB cordless keyboard & mouse. I tried a Belkin, Tripp-Lite, and IOGear; all would lose or mess up the tracking for both the K & M when I switched away to my other box.I have a Logitech Cordless Elite Duo, it has one USB plug that goes to the receiver for the K & M. I think that is what's screwing the KVM switches I've tried, as they apparently need seperate plugs for both.
johnsonx - Wednesday, October 19, 2005 - link
I think your issue is that when you switch your USB device looses power for a moment... that's enough to kill the wireless receiver and make it loose track of the kb and mouse.