View Full Version : Hypersensitive iMac/iRack VGA

09-03-2002, 03:14 PM
Hey everyone.

Got an interesting one for ya! I took an iMac DV 500 MHz model and stuck the motherboard in a Marathon iRack that they just started selling, plugged the external VGA into an NTI KVM switch that has a 15" Sony CRT and guess what... no video. I then plugged the VGA into a 17" Sony CRT and guess what, I got video. Plugged the 17" Sony into the KVM and got no video. Plugged the 15" directly into the VGA of the iMac, and no video. The only thing I could use my new iRack iMac with is a stand-alone 17" CRT which really sucks since I can't plug it into a KVM switch, which was 90% of the reason I bought the rack kit in the first place.

I then noticed on Apple's help site that only "certain" types of video are supported by the iMac's VGA out. I'm wondering if these "certain" types exclude KVM's.

Has anyone else run into this? Is there any 3rd party devices that can help? I tried a Dr.Bott gHead, but that didn't work either. Are there any hacks that can be done?

09-03-2002, 07:51 PM
That seems a bit odd - did the video problem only occur when you hot-swapped the cables? or was this after a hard restart?. You may have to ensure that that the KVM is set to point to the monitor when you restart.

Seems odd to me - I know I had no problem w/ the old manual style VGA switch box when I was toggling between a Dell and a Mac....


09-04-2002, 07:30 AM
Yeah, a hot swap worked, but that is only because it thought it was still plugged into the 17" monitor. The thing is, this machine has a kick-off unit attached and as soon as that sucker fires, forget about video. Unless I keep it plugged into that 17" monitor.

No luck with that KVM trick. I tried a sequence where it was all OFF, then turn Monitor on, turn KVM on, set KVM to the channel of the iMac, then turn iMac on, but still no luck. I'm wondering if there is a DIP switch setting I need to use with that NTI KVM switch.

09-08-2002, 12:46 AM
you might want to check out gHEAD ( http://drbott.com/prod/db.lasso?code=0101-GHED ) I have a couple and they often help in situations like this.

basically the thing tricks the mac into thinking a monitor is connected even when one is not, allowing you to boot with a KVM attach and turn to a different computer.

- Chris

09-08-2002, 07:18 AM
I bought one (three actually) gHeads. But it doesn't work for the video card that comes with the iMac. Basically, the iMac allows 3 resolutions and that's it - no more. You can't trick the card into giving you any more than that. I think I've point pointed it down to the NTI switch. I called their tech support and they said that this was a 'known problem' and that they are working on an adapter to fix this. I'm guessing when the iMac boots, it's looking for a very specific refresh rate (95Hz) and the NTI switch cannot pass back that information through it from the monitor. However, a Dr. Bott switch can. So, I guess I'm going to have to stick with Dr. Bott KVM's for a while.

09-11-2002, 02:34 AM
So what do you think of th iRack, now that the mystery has been solved? Any pros or cons that were not as expected?

09-11-2002, 08:42 AM
Well, the first problem I encountered was the way the RAM has to be set. You have to put this 'adapter' in the iMac's ram slots to that the ram sits parallel to the logicboard. The only catch is, in order to put the ram adapter in, you have to remove the little yellow clips from the existings ram slots. This required some technique and a lot of aggrevation, and you can wind up chewing up the sides of the slots by doing this. Let's not forget that one slip could cause your screwdriver to go scraping across the logic board. It would have been a lot better if Marathon had just made the adapter to fit with the clips.

Another thing is that the rack kit uses the Reset button (on the side of the iMac) as it's start/restart button. So, sometimes when I think I'm restarting the iRack, I'm actually putting it to sleep. Too often I'm having to use the ON/OFF switch at the back to restart it, which is a real pain when it is screwed into a rack case where it's hard to get at the back.

Now, it was cool that they put USB and Firewire access on the front and back of the iRack as well as the back. However, in order to activate these front ports, you have to go out and buy two jumper cables to connect them to the iMac's existing ports. You would think after spending over $600 for the kit that they would include patch cables.

Also, the rack ears cannot be moved back for center-mounting. The rack that I have mounts all the units in the middle, so it appears quite recessed when compared to my other rack units. I'm also a little unsure about the entire weight of the iRack being carried by two little racks ears in the front. I can just imagine it slowing bending down in the back after a year or so.

The whole idea of this rack kit is definately cool. I think, in time, these kits will be more refined. I'm guessing Marathon was pressured into putting something together and didn't really have enough time to think it through. Hopefully the next version will include fixes to the problems I had.

09-11-2002, 12:05 PM
Thanks for the insight. I checked out the old version for a tray loader board about a year ago, but wanted the firewire. Too bad there isn't a way to add a PCI slot or a SCSI contoller...

$600? I thought they were like $399. What else does one need besides the cables you metnioned and of course the imac board?


09-11-2002, 12:28 PM
$600 Canadian, I guess I should have been more specific. You will need a monitor that can do 800 x 600 at 95Hz for sure or else the video will cut out, but that should be it. Also, avoid using NTI's switches and stick with Dr. Bott until NTI gets their problems sorted out.

09-15-2002, 02:28 AM
Great. I already have the 8 way USB Dr. Bott switch - 1st time in my life I "won the toss" I think...

Thanks for the help.