Sunday, April 12, 2009

Level One DVI PS/2 KVM-0406 vs nearly everything else I tried to hook up to it

DVI PS/2 KVM switches are very hard to come by. Most digital video KVM switches use the USB interface these days, not the older PS/2 keyboard and mouse interface. Most computers for the last decade have featured USB connectors, though not all of them support USB keyboard and mice at boot time. Unfortunately, one of my machines is an embedded system, a Roland VS-2400CD, which features only PS/2 connections, and cannot be upgraded to USB since there are no expansion slots of any kind, and even if there were, it would also require firmware to support it.

One would think that such an issue could be resolved by the use of a simple PS/2 - USB converter. But that is not so. Plenty of converters exist to connect PS/2 keyboard and mice to USB-only computers, but there are no converters that I know of that will allow PS/2-only computers to use USB device.

In fact, the only solution is a smart KVM switch that can accept the PS/2 on the computer port side. That presents a big problem if one also wants to use a digital video interface like DVI or HDMI, since very few digital KVM switches exist with a PS/2 interface.

A week ago, I found one such switch on ebay. It was a Level One model KVM-0406 . The price was ridiculously low - about $45 shipped. The specs said its maximum resolution over DVI was 1600x1200, which was lower than the 1920x1200 resolution that I needed. But it also said that it supported the maximum single-link DVI bandwidth of 165 MHz, and my video card is doing 1920x1200 over single link DVI. So, I ordered it, and received it by fedex on saturday April 11.
I immediately hooked up one of my PCs to it, which was using an nVidia 8600GT video card. The pleasant surprise was that it ran just fine at 1920X1200. The mouse and keyboard worked just as well as with my previous analog KVM switch, too. The only problem was that the Cyberlink Blu-ray advisor noticed that HDCP did not work on the DVI connection - where it worked without the switch, but I did not have the expectation that this old switch would support it.

I thought I was all set and I went on running errands for the day - not trying to connect the 2 other machines to the switch.

Much later in the day, I was cursing at the switch. The Roland VS-2400CD had some major issues with the mouse locking up and jumping all over the place by itself. This was something that could only be attributed to the mouse emulation in the KVM switch.

Worse, my second PC, using an nVidia 9500GT video card, had major problems with it when connected to the switch. When I first hooked it up, "live", the display at 1920x1200 just flickered horribly and the picture was half way off screen. I thought it might be the 15ft cable. So I switched to a 6ft cable (the same length as for the other PC that worked), and brought the machine closer. The problem persisted.
I tried to reboot the system. The BIOS screens showed up without corruption. But the operating system (Vista) would not boot. Not from the hard drive, nor from the installation DVD !
I never could figure out why that was. But when I took the KVM switch out of the way and reverted to the previous configuration, the machine booted just fine.

Needless to say, with only 1 machine out of 3 working properly with the switch, it is not useful to me, and I'm in the process of trying to return it. I am not sure if I will have any luck locating a good PS/2 and DVI/HDMI switch.

For now, I have reverted to using my trusted Iogear MiniView SE for the keyboard and mouse connections, since it works properly with all 3 machines and its mouse emulation does not cause issue. And I am using the previously-discussed Monoprice HDX-501 switch to switch the Gateway FHD2401 digital display. It's not very ergonomic, especially since the HDX-501 uses a single toggle button that only goes forward, and requires four button presses to go to the previous input :-(. I foresee a better digital switch in my future.

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