Member Avatar for graceawong

A bit of a weird problem here... I recently purchased an ioGear digital KVM (GCS1644) that supports a dual monitor setup (I'm currently running two 23" monitors - an older Samsung and a new LG). I got my first PC up and running without a problem, but the second one is giving me all sorts of grief. This is what I did in order:

1) I had been using only onboard video via DVI-D on an older KVM switch (for single monitor only), and it worked just fine. Since I needed dual DVI for the new KVM to work, I tried using a VGA-->DVI adapter in the KVM end and into VGA on the motherboard. Nada.

2) I purchased an nVidia GT 620 video card (with 2GB onboard RAM) and installed it. In the past, I've never needed to install the drivers before plugging in my monitor; I would just put up with 640x480 resolution until I did get the drivers installed. Well, that didn't happen here; in fact, nothing showed up on my monitor at all. So I moved it back to my workbench and plugged it into an old bugger monitor that only had VGA (not even widescreen - horrors!! :)), and it worked just fine, so I used that opportunity to install the new drivers. No problems. I checked Device Manager, just in case, and yup - video card detected just fine.

3) I moved the PC back to my desk, and zilch - nothing. I tried plugging it into the other KVM slots (it's a four PC KVM), and still nothing (I 'm not sure if it matters, but the new video card and the KVM only support DVI-I). Oh, and incidentally, the reason I knew the PC was running okay was because I could VNC into it, no problem.

4) I unplugged all the KVM cables from both the switch and the PC and tried plugging directly from both monitors into the available DVI slots (both onboard and video card), and zip. So I borrowed my husband's monitor (temporarily, of course... :)) and tried plugging that into all available DVI slots and still nothing.

Suffice it to say, I've hit the "really pissed off" phase. I'm going to try swapping out for another video card once I hit the computer store later, but if that doesn't work - well, I'm at a loss. It is an older PC but has never given me grief before. I am wondering, though - would compatibility be an issue?? As I said earlier, the onboard DVI is DVI-D, which is, as I understand it, an older generation of DVI. And is it possible that the motherboard doesn't support DVI-I because it is older??

Any help would be appreciated, because I've got a very bad feeling about this (as in a have-to-replace-motherboard-CPU-and-RAM-very-bad-feeling-about-this). I am running Windows 7 Ultimate.

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Good news: your symptoms line up with a simple mismatch, not a dead board. The GCS1644 is a digital DVI switch that expects two DVI video outputs from each PC and two DVI inputs on the monitors. It ships with DVI‑D cables and relies on EDID/DynaSync for the handshake. A passive VGA->DVI dongle will never light up this KVM because DVI‑D carries no analog signal. Use only digital feeds (DVI or HDMI via HDMI‑to‑DVI), and wire both heads from the same PC into Port A and Port B on the KVM. Port A is the primary head. (iogear.com)

On the GT 620 specifically, most cards expose one DVI, one HDMI, and one VGA. For dual display into this KVM, run the card’s DVI to KVM Port A and the card’s HDMI (with an HDMI‑to‑DVI cable) to KVM Port B. Avoid the motherboard’s VGA unless you enable the iGPU to coexist with the add‑in card. (techpowerup.com)

Quick checklist that usually fixes “no picture” on this model:

  • Cables: use straight DVI‑D (or HDMI‑to‑DVI) only; no VGA adapters. Seat DVI fully on Port A and Port B. (iogear.com)
  • Power‑up order: with both monitors on, power the KVM first, then boot the PC so EDID is captured cleanly. (cdn.shopify.com)
  • If mixing onboard + discrete graphics, enable “iGPU Multi‑Monitor” (or similar) in BIOS; many boards disable the iGPU when a dGPU is present. (intel.com)
  • In Windows, once you have a signal, set up Extend across both displays; the KVM will remember via DynaSync when you switch ports. (iogear.com)

+1 to : KVMs really do not like passive converters. If you must drive a VGA‑only screen from a DVI‑D source, use an active DVI‑D to VGA converter instead of a passive plug. (bhphotovideo.com)

If you try the above and still get black screens, test each GPU output directly to a monitor with the same DVI cable, then reinsert the KVM in between. That will isolate a bad cable vs. a handshake/wiring issue.

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Member Avatar for caperjack

my experience with kvm switches is they don't like converter adapters ,and I have owned 4 different kvm's

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