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Q about KVM
I am looking at KVMs on EBAY - will choose DVI this time. I notice
the pics show only one USB to support mouse and keyboard. How do they get away with that? My mouse and keyboard each has its own USB connector. and right now needed two ports on my defunct IOGEAR VGA KVM is why I ask. Thanks Al |
#2
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Q about KVM
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#3
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Q about KVM
Turing wrote:
I am looking at KVMs on EBAY - will choose DVI this time. I notice the pics show only one USB to support mouse and keyboard. How do they get away with that? Multiple devices can connect to the same USB port. That is how, for example, passive USB hubs work: many ports to one port. The USB port can only support a fixed amount of power, so how many USB devices you can connect to the port depends on whether they are low- or high-power USB devices. Keyboards and mice are low-power USB devices. A single USB controller can manage up to 127 devices (7 bit address = 2^7 addresses = 128 addresses, but the host controller gets one). To get that many chained together means having to use powered USB hubs (they have their own source of power, like an A/C adapter). A hub itself counts as a device. While I've seen 10-, 20-, and 30-port powered USB hubs that you could chain together (four 30-port hub + one address for each hub = 124 addresses) at newegg.com which get pretty pricey, I didn't bother hunting around for one with 126 ports (126 ports + 1 for itself for the 127-port maximum). I did happen to find the following: 97-port USB hub https://www.youtube.com/watch?v=4OS6L80Fe3Q 16 7-port powered USB hubs = 112 ports minus 16 ports to chain them together = 96 ports, so I don't know how they get a count of 97 unless they're counting the downstream port+cable to the computer. Whether such a frankenjob works on your computer depends on its USB host controller's capabilities. As the video show, plug-n-play detects takes a long time to discover all those ports. Remember those old movies showing a telephone switchboard manned by many telephone operators? Large-numbered USB ports chained together would make the same mess. You'd probably want Bluetooth or wi-fi devices instead of the cost of such a hugh-ported USB hub and all those USB cables and the space for it all. You didn't give a URL to the KVM with just one USB port for both keyboard and mouse. Perhaps in its description is listed a Y-adapter cable: 2 USB ports to 1 USB port. Those have been around a long time. I remember using one for an external USB HDD that needed to use 2 ports because the drive needed more power than one port could deliver. In that case, I was using 2 USB ports for 1 device. In your case, the Y-adapter would go the other way: 2 devices to 1 port. Maybe the KVM comes with a passive or powered hub that lets you connect more than 2 input USB devices to the KVM. We don't know because you didn't show us (by giving a URL). Tough to explain something that is vague. |
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Q about KVM
On Mon, 5 Nov 2018 11:43:46 -0500, John McGaw wrote:
On 11/5/2018 9:59 AM, wrote: I am looking at KVMs on EBAY - will choose DVI this time. I notice the pics show only one USB to support mouse and keyboard. How do they get away with that? My mouse and keyboard each has its own USB connector. and right now needed two ports on my defunct IOGEAR VGA KVM is why I ask. Thanks Al Which one are you looking at, specifically? Mine has a single USB on the front and two on the back for keyboard and mouse There are many. One is: https://www.ebay.com/itm/KVM-Cable-f...0~:rk:197:pf:0 I guess I am confused. You see my present, now defunct, KVM is VGA, and the VGA cables connecting each PC to the KVM connect the mouse and keyboard capability with USB attachments on said cables to both (plus sound cables). And of course, the mouse and keyboard themselves connect to the KVM too. That's how the mouse and keyboard reach each PC. So far I do not see that on the DVI models. I think I see (on the DVI) just one cable, printer on one end, USB on the other. Also sound cables tho. So I have no idea how the mouse and keyboard each reach the PCs via a DVI KVM. Unless it is thru the DVI itself? Thanks for your response. Al |
#6
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Q about KVM
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