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Johnny
Fed Up. Bye.
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join:2001-06-27
Atlanta, GA
kudos:2

[Parts Check] Does anyone know why my KVM does this?

Hey,

Below is a message I sent to IOGEAR to see if I should buy a KVM that supports a bigger resolution. Basically, my Dell Optiplex 780 SFF with a DVI card works fine through the IOGEAR 2-port switch noted below, but the Mac Pro (Radeon x1900XT) does not.

Without the switch, the Mac Pro works fine with the display.

Just wondering if anyone had this KVM switch or knew why it won't drive the display from the Mac (but will from the PC). Thanks

Message I sent to IOGEAR tech support:

I currently have an IOGEAR GCS932UB KVM switch, which works fine to share my 20-inch Apple DVI display between a Dell PC and an original Mac Pro. I recently bought an Apple 27-inch LED Cinema Display and connected it up to the IOGEAR. The IOGEAR displays the PC video fine, but will not display any video from the Mac Pro (Radeon X1900 XT card).

IMPORTANT: I am using a ATLONA DVI-to-mini-Displayport converter to connect the IOGEAR to the LED Cinema Display. As above, this works with the PC but not the Mac.

There is nothing wrong with the monitor, or the Mac, as if I REMOVE the KVM switch from the setup, and plug the Mac directly into the Apple LED Cinema display through the ATLONA converter, it works perfectly.

So my question is, is the IOGEAR GCS932UB KVM switch which I am using not sufficient to drive the Apple 27-inch LED Cinema Display? If that seems to be the issue, then I will buy a new IOGEAR switch.

Will the IOGEAR GCS982U switch (with its higher resolution support) drive the Apple display through the DVI-to-miniDisplayport adapter?



signmeuptoo
Bless you Howie
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join:2001-11-22
NanoParticle
kudos:5

Sure wish I could help you. I think the OS is the issue though.


sk1939
Premium
join:2010-10-23
Mclean, VA
kudos:10
reply to Johnny

The question is, what resolution are you driving the displays at? My Avocent doesn't have an issue with either my Optiplex or the Mac Pro.


antbhill2
Premium,MVM
join:2001-02-28
Northern VA
reply to Johnny

Agree with SK1939. Rated resolution of the KVM switch is 1920 X 1200. It appears your monitor is capable of 2560-by-1440. So you may have to reduce the resolution to use that switch.



Camelot One
Premium,MVM
join:2001-11-21
Greenwood, IN
kudos:2

said by antbhill2:

Agree with SK1939. Rated resolution of the KVM switch is 1920 X 1200. It appears your monitor is capable of 2560-by-1440. So you may have to reduce the resolution to use that switch.

I have the same problem with my Dell 30". None of the cheap KVMs I have on hand can pass it's native 2560x1600.

For that matter, most of the DVI to Display Port adapters I have seen are single link, not dual. (and I think at 1560x1440, you would need dual link DVI.)


drew
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Port Orchard, WA
kudos:6
reply to Johnny

The above are correct - the KVM can't drive that resolution.
IOGEAR has a KVM (»www.iogear.com/product/GCS1212TAA/) that'll do it... spendy.

Searching for dual-link kvm shows a high price tag.
--
flickr | Of faith, power and glory


sk1939
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Mclean, VA
kudos:10
Reviews:
·T-Mobile US
·Verizon FiOS

1 edit
reply to Camelot One

said by Camelot One:

For that matter, most of the DVI to Display Port adapters I have seen are single link, not dual. (and I think at 1560x1440, you would need dual link DVI.)

Well sort of. Single-Link DVI will handle resolutions up to 2,098 -1,311 @ 60 Hz, but only IF the clock frequency is 165Mhz or lower and has at most 24 bits per pixel. Otherwise modes that require more than 24 bits per pixel, and/or 165 MHz pixel clock frequency use the Dual-Link mode.

For example, Single-Link will support a display resolution of 3,840 - 2,400, but only at a slideshow refresh rate of 17Hz. Dual-Link by comparison will support the same resolution at a more playable 33Hz.

Your monitors resolution of 2,560 - 1,600 uses two 135 MHz channels, so Dual-Link is required for the maximum resolution. Also note that your adapter ( ATLONA DVI-to-mini-Displayport converter) only supports resolutions up to 1920x1200. Likewise, your KVM only supports resolutions up to 1920 X 1200 @ 60 Hz with 32 bit color.

As far as a new KVM goes, I suggest this one: »www.newegg.com/Product/Product.a···17791101

Edit: IOGear makes two alternative options for a considerably cheaper price.

»www.amazon.com/IOGEAR-2-Port-Dua···4&sr=1-6

»www.amazon.com/IOGEAR-2-Port-Dua···4&sr=1-3

You will also need an updated version of your adapter (you have the AT-DP200): »www.amazon.com/ATLONA-AT-DP400-D···2&sr=1-1


Johnny
Fed Up. Bye.
Premium
join:2001-06-27
Atlanta, GA
kudos:2
reply to sk1939

said by sk1939:

The question is, what resolution are you driving the displays at? My Avocent doesn't have an issue with either my Optiplex or the Mac Pro.

That's gotta be the key. I think XP doesn't try to offer anything more than the IOGEAR can handle, whereas the Mac will use the full display capability, which is too much for the switch.

I am using the Atlona DP-400, and as I said, with the KVM switch out of the loop, that works fine, full resolution, even my ancient MacBook Pro (2007) can drive the 27" and mirror, no problem.

This confirms my suspicion that I need to buy a new switch. PC works, Mac works, display works, and the Atlona works, so a new switch is in order.

Thanks to all. As soon as I get the new switch I'll check back.


Johnny
Fed Up. Bye.
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join:2001-06-27
Atlanta, GA
kudos:2
reply to sk1939

said by sk1939:

Your monitors resolution of 2,560 - 1,600 uses two 135 MHz channels, so Dual-Link is required for the maximum resolution. Also note that your adapter ( ATLONA DVI-to-mini-Displayport converter) only supports resolutions up to 1920x1200. Likewise, your KVM only supports resolutions up to 1920 X 1200 @ 60 Hz with 32 bit color.

»www.amazon.com/IOGEAR-2-Port-Dua···4&sr=1-6

Thanks for the reply. Going to order the GCS982U switch - I don't need 7.1 audio. Hopefully can try it out in a few days.

My Atlona is already the DP-400 one, so I'm set there.

I didn't see an IOGEAR switch that came with mini-displayport output. If anybody saw one, please let me know.

sk1939
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The only one I've seen that even use's DP is this Geffen: »www.newegg.com/Product/Product.a···DP%20KVM , and that's not mini-DP, just regular DP.



Johnny
Fed Up. Bye.
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Atlanta, GA
kudos:2

No biggie. I'm just glad I didn't have to get a new Mac Pro yet, because nobody knows if there is even going to be one. New switch should be here end of week.


sk1939
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Mclean, VA
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Reviews:
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·Verizon FiOS

Certainly saves you on making a major purchase. You many also want to consider picking up one of these for future use: »www.newegg.com/Product/Product.a···12200691

That being said, how do you like the new Cinema compared to the older revisions? I'm not a fan of the price tag, but I am curious quality-wise.



Johnny
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Atlanta, GA
kudos:2

Very sharp, I like the glossy (don't know why, but I do), built-in camera recognized by the Mac so I don't have to whip out the iPad for video conference, has a MagSafe cable so I can power my MacBook Pro while using it for mirroring in case the desktop goes down, and the usual 3 USB ports. Have to see if those ports have enough oomph to charge the iDevices.

Usually I get a refurb, but there weren't any available at the time I picked this up in-store. The refurb is $849 I believe.


sk1939
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Mclean, VA
kudos:10

See, I don't care for the glossy screens mostly because I can't stand the glare they give off in direct light. How is the color?



Johnny
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Atlanta, GA
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Much richer than the old 20" this is replacing. I suppose that is true for any upgrade of a display over the years. There's no yellow cast that some new displays have been said to have.


sk1939
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join:2010-10-23
Mclean, VA
kudos:10

Nothing can compare to the old CRTs though as far as refresh and black levels.

I hadn't heard that. I personally am looking at the HP Dreamcolor, although it's still rather pricey for my taste.



Johnny
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Atlanta, GA
kudos:2

Continuing this saga - I received the IOGEAR GCS982U switch. Swapped it in for the other switch, and now with both PC and Mac connected, the Mac display works. Sort of. I'm thinking there is some setting in the switch that I had made with the other one and I need to make with this one.

- the PC doesn't display anything at all. Nada. Strangely, it did with the other switch and the exact same setup. The switch's LED shows 2 PCs connected.

- Switching to the PC, and then back to the Mac, now results in a dead screen. I have to press the Reset button on the ATLONA PCI converter to get the display back. I have no idea what's causing this. It was NOT an issue with the 932U switch.

So - still not a smooth setup. I can use my monitor with the Mac through the switch now (unlike before), but these new issues arise.

1. Does anyone know what I might need to do on a Windows boot to set something about the display? I know zero about Windows.

2. Does anything come to mind as to what might cause a PC not to want to display through this switch, when it DID display through the other (lower-res) switch? Any KVM settings that I need to flip?

3. Any other tips greatly appreciated.



drew
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Port Orchard, WA
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What resolution ( and connection ) is the PC using? I am concerned about resolution that the PC is running is whacked out.
--
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Johnny
Fed Up. Bye.
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Atlanta, GA
kudos:2

said by drew:

What resolution ( and connection ) is the PC using? I am concerned about resolution that the PC is running is whacked out.

DVI, to the switch. Well, I can't really tell the resolution since the PC isn't on the display. Can I boot it into a mode that will display no matter what, and set the resolution from there? It always says something about F12 when it boots...


Johnny
Fed Up. Bye.
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Atlanta, GA
kudos:2
reply to drew

OK, I put a separate keyboard on the Dell, hold down F12, and I can get it to proceed to the "Windows XP" progress bar that appears right before the desktop should start loading, but nothing beyond that.

And, every time I switch back to the Mac after the PC has a blank screen, I have to reset the DVI-to-miniDisplayport converter.

What settings should I make, or how do I boot the PC in "default video" mode?



drew
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Port Orchard, WA
kudos:6

Can you take the new switch out of the equation and plug the display directly into the PC? Then, hopefully, it will display properly. You can then set the resolution to something small, like 1024x768, that will, for sure, work through the switch.
--
flickr | Of faith, power and glory



Johnny
Fed Up. Bye.
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Atlanta, GA
kudos:2

Will do. I JUST NOW finished switching everything back to what works. Gotta wait until tomorrow afternoon though - had to reset everything since I can basically only switch to the 27" on weekends. I just need to test now if the PC works at all with the new switch, even with the small monitor. If it doesn't, I'm screwed.

Addendum: PC works with new switch, and 20" DVI monitor. Does not work with new switch, 27-inch monitor and DVI converter. Keyboard repeat is very slooooow though - I remember having this issue with the other switch when it was new. There is some way to set it not to emulate a keyboard..

Addendum: checked the PC and it is set for 1280 x 800. Not sure if I can work with it set to 1024, as custom app is written badly and very sensitive to resolutions. Will try and post back.

Thank you Drew.



Johnny
Fed Up. Bye.
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Atlanta, GA
kudos:2
reply to sk1939

Well, in addition to my difficulties getting the big display to work, now I have somehow torqued up the switch. It flashes 3 short and one long when I switch it to the Mac, and all USB is frozen. When I switch back to the PC, Windows cheerfully advises that I could use a "faster USB port than the one I am connected to." But at least after that, the PC unfreezes and I can work. The Mac is still totally frozen even with a restart.

I disconnected the switch from both computers and left it that way for 30 minutes - no change.

Anybody know what this "three dots and one dash" flashing code means? IOGEAR's user manual really sucks.



Johnny
Fed Up. Bye.
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Atlanta, GA
kudos:2

Well, I'm sending the switch back. Somehow it just isn't compatible, even when using the Apple 20" monitor.

I went back to the GCS932 switch and it works fine with the same computers and same monitor.

I wonder if this could have been due to the Dell having single-link DVI or something like that? I'm also willing to put a different GPU in the Dell if I only knew what to put.

Now looking at the Startech switch - it also claims 2560 x 1600 res and has good reviews.



drew
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Port Orchard, WA
kudos:6

In looking at the 780 specs, I only see a VGA and Display Port output for video... how are you getting DVI? Are you using an expansion card? If so, what card?
--
flickr | Of faith, power and glory



Johnny
Fed Up. Bye.
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Atlanta, GA
kudos:2

said by drew:

In looking at the 780 specs, I only see a VGA and Display Port output for video... how are you getting DVI? Are you using an expansion card? If so, what card?

Yes, I upgraded it a year ago. Radeon HD 4500 Series. The one that came with it sucked for this 20" display. I can't open up the machine right now to get the exact model, but it has 512MB of display memory.

I just found out that the "Adapter" section of the Display Control Panel has some resolution settings. NOW they tell me... after I already got an RMA.

Probably doesn't matter, as the in-house app that I have to run for work chokes if you adjust anything - windows overlap the damn taskbar, windows-within-windows drive me nuts, etc.


drew
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Could you run GPU-Z for me?

»www.techpowerup.com/gpuz/



drew
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reply to Johnny

The Radeon HD 4500 is a mobile platform. I think it's probably a HD 4550.

From AMD's site on the 4550

quote:
*Two integrated DVI display outputs
-Primary supports 18-, 24-, and 30-bit digital displays at all resolutions up to 1920x1200 (single-link DVI) or 2560x1600 (dual-link DVI)2
-Secondary supports 18-, 24-, and 30-bit digital displays at all resolutions up to 1920x1200 (single-link DVI only)2

The superscript 2 has the following note:

quote:
2.Some custom resolutions require user configuration
The biggest thing that stands out to me is that one of the two ports on the video card only supports dual-link DVI.

I would consider un-packing the switch and seeing if you can make it work with that in mind. Another thing I would look at is cables/adapters.

And I will say this - what the heck Windows/Video Card Manufacturers? This should NOT be this complicated.
--
flickr | Of faith, power and glory


Johnny
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Atlanta, GA
kudos:2
reply to drew

said by drew:

Could you run GPU-Z for me?

»www.techpowerup.com/gpuz/

Gimme a couple of minutes - the PC is on a VPN so I have to mail this to myself and I may have to kill the VPN to even get to the internet.


Johnny
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Atlanta, GA
kudos:2
reply to drew

I have no idea where it downloaded it to. Where in the hell in IE do you find the list of recently downloaded files?

Start->Search->All Files and Folders -> Filename contains "GPU-Z"

Nothing so far. Didn't find it.