Gefen DVI DL: Dual Link DVI + USB KVM
by Anand Lal Shimpi on October 19, 2005 12:05 AM EST- Posted in
- GPUs
DVI-DL Operation and Issues
One of the most popular uses for the Gefen DVI DL is to switch between a Mac and a PC, hooked up to an Apple 30" Cinema Display, and that is the very configuration that we're looking to test today.
Connected as system 1 was the Powermac G5, with an ATI Radeon 9600 Pro Mac & PC Edition, and system 2 was a PC with a NVIDIA GeForce 7800 GTX. The 9600 Pro Mac & PC Edition has one dual link DVI port, and thus, has no problem driving the 30" display, as does the GeForce 7800 GTX in the PC.
Now, the 30" Cinema Display has its own 2-port USB hub built into the back of the unit, and that was the hub that we had plugged into the Gefen unit. The keyboard and mouse were plugged into the Cinema Display's 2 ports. The problem with this arrangement was that when switching back and forth between Windows XP and OS X, the USB interface would always drop out when switching back to the Mac. The USB devices that we had hooked up to the DVI DL were an Apple USB keyboard and a Logitech MX1000 mouse, so whenever we'd switch back to the Mac, there would be no keyboard or mouse support. By plugging the keyboard and mouse directly into the two ports on the DVI DL, we averted the problem (we later fixed the problem through another method).
By default, the DVI DL does have some stipulations that you have to work with in order to actually get the switcher to work. First and foremost, you cannot switch to any machine that you haven't booted while switched to. For example, with both the Mac and PC connected to the switch box, I started the G5 up and I was switched to it. If I had turned the PC on while still being switched to the G5, I would not get any display on the PC. In order to turn the PC on, I would have to switch over to the PC, then turn the machine on and wait for it to boot.
With both machines up and running, it was time to give the DVI DL a try. Starting on System 1 (the Mac), we hit the Select button and switched over to System 2 (the PC). Ta-da, it worked. Now, time to switch back, but unfortunately, switching back wasn't as smooth of a process.
The screen had artifacts all over it and the mouse cursor had turned into one giant block.
We contacted Gefen, which offered extremely quick turn-around on all tech-support queries (generally, all questions were answered within 24 hours on their forums). Gefen insisted that if we wanted a solution to the problem, we would have to purchase a DVI Detective. Gefen's DVI Detective is a programmable device that records your monitor's EDID information and constantly transmits it to the computer to which it is connected, so regardless of whether or not the monitor is actually connected to it, the computer thinks that it is.
Given the price of the DVI DL switcher, the functionality of the DVI Detective should honestly be built into the device, but for whatever reason, it isn't. Granted, this isn't exactly Gefen's fault, but rather a problem with the way that OS X in combination with the ATI Radeon 9600 Pro handle a disconnected DVI signal, as the PC worked just fine. But given that a number of 30" Cinema Display owners may be turning to the DVI DL, it is an issue that is worth noting.
One of the most popular uses for the Gefen DVI DL is to switch between a Mac and a PC, hooked up to an Apple 30" Cinema Display, and that is the very configuration that we're looking to test today.
Connected as system 1 was the Powermac G5, with an ATI Radeon 9600 Pro Mac & PC Edition, and system 2 was a PC with a NVIDIA GeForce 7800 GTX. The 9600 Pro Mac & PC Edition has one dual link DVI port, and thus, has no problem driving the 30" display, as does the GeForce 7800 GTX in the PC.
Now, the 30" Cinema Display has its own 2-port USB hub built into the back of the unit, and that was the hub that we had plugged into the Gefen unit. The keyboard and mouse were plugged into the Cinema Display's 2 ports. The problem with this arrangement was that when switching back and forth between Windows XP and OS X, the USB interface would always drop out when switching back to the Mac. The USB devices that we had hooked up to the DVI DL were an Apple USB keyboard and a Logitech MX1000 mouse, so whenever we'd switch back to the Mac, there would be no keyboard or mouse support. By plugging the keyboard and mouse directly into the two ports on the DVI DL, we averted the problem (we later fixed the problem through another method).
By default, the DVI DL does have some stipulations that you have to work with in order to actually get the switcher to work. First and foremost, you cannot switch to any machine that you haven't booted while switched to. For example, with both the Mac and PC connected to the switch box, I started the G5 up and I was switched to it. If I had turned the PC on while still being switched to the G5, I would not get any display on the PC. In order to turn the PC on, I would have to switch over to the PC, then turn the machine on and wait for it to boot.
With both machines up and running, it was time to give the DVI DL a try. Starting on System 1 (the Mac), we hit the Select button and switched over to System 2 (the PC). Ta-da, it worked. Now, time to switch back, but unfortunately, switching back wasn't as smooth of a process.
The screen had artifacts all over it and the mouse cursor had turned into one giant block.
That big block? That was our mouse cursor.
We contacted Gefen, which offered extremely quick turn-around on all tech-support queries (generally, all questions were answered within 24 hours on their forums). Gefen insisted that if we wanted a solution to the problem, we would have to purchase a DVI Detective. Gefen's DVI Detective is a programmable device that records your monitor's EDID information and constantly transmits it to the computer to which it is connected, so regardless of whether or not the monitor is actually connected to it, the computer thinks that it is.
Given the price of the DVI DL switcher, the functionality of the DVI Detective should honestly be built into the device, but for whatever reason, it isn't. Granted, this isn't exactly Gefen's fault, but rather a problem with the way that OS X in combination with the ATI Radeon 9600 Pro handle a disconnected DVI signal, as the PC worked just fine. But given that a number of 30" Cinema Display owners may be turning to the DVI DL, it is an issue that is worth noting.
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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.