VOGONS


KVM Switches

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First post, by McBierle

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Hi People!

Do you use or have experience with KVM switches?
The first i just bought is a 2-way ps/2 switch with audio. The mouse wouldn't work 🙁 ;i read something about ps/2 and serial not necessarily beeing truly compatible. Another without audio is working.
I still have a 4-way switch i diddn't test yet.

Anyways what i really want to have is:

- 3-way switch
- ps/2 or better Serial/DIN
- audio
- manual switch, no need for fancy hotkeys

What are your experiences?

Reply 1 of 22, by Unknown_K

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If you need to switch audio I suggest you use Belkin SOHO KVM switches. I have used them since they made serial port models and still use them today with USB+DVI.

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Reply 2 of 22, by BushLin

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The old Belkin Omniview KVM switches without built-in cables were great for VGA and PS/2 if you didn't want to spend big on enterprise equipment. They were commonplace around 15 years ago and if you bought the better cables the picture wasn't compromised much. I believe they did offer some like this with audio as well but I preferred the design of the heavier ones where they sit flat and don't move about. There's a buttons for switching or by hotkey where you can specify the numbered input.

They followed these up with more modern USB models which had issues with switching reliably and super cheap options with built in cables which were apparently not very good.

EDIT: Here's the older Omniview with audio.
https://www.ebay.co.uk/itm/Belkin-OmniView-SO … wwAAOSwgb5c6PC2
I actually remember these, if you use the proper cables the weight at the back is too much, sort of pulling itself over; however, if you somehow deal with the bad vertical design choice (we hung the cables above for these) they work as well as any other Belkin switch. I'm not saying buy this by any means but the cables pictured are the correct ones to use for all the "proper" Belkin switches.

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Reply 3 of 22, by mothergoose729

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I have an IOGEAR GCS614A. It supports switching with keyboard input, which is pretty cool, but I haven't yet got enough computer running at the same time to really test it out much. It also will switches to whatever port happens to be on (scan mode), which has worked for me pretty well so far.

Reply 4 of 22, by SirNickity

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McBierle wrote:

The mouse wouldn't work 🙁 ;i read something about ps/2 and serial not necessarily beeing truly compatible.

They're not compatible at all. There are a certain number of PS/2 mice that can auto-detect serial hosts and change modes with a suitable physical adapter, but that's the exception, not the rule. Also you need the specific adapter that connects the pins in the order that particular mouse expects. Random ones found in a stash or on Ebay may or may not work.

I always used IOGear KVMs as well. They're decent for the cost. Not quite as nice as the enterprise stuff I would use at work, but it's never been something I was willing to put $1000s into. Too rich for my blood.

Reply 5 of 22, by eisapc

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I experienced some flaky behaviour while using older keyboards with high current draw. Using a powered KVM-switch fixed the problem.
Currently I use Compaq KVM, Belkin, Digitus and Aten.

Reply 6 of 22, by Tiido

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I have a D-link DKVM-8E and I'm mostly fine with it except that sometimes it forgets that ALT, SHIFT or CTRL was released and you have half messed up keyboard input. This makes games difficult sometimes. Older version of this KVM can do serial mouse to PS/2 translation but I have no clue how effective it is.
I have a few 4 and 2 port ones but I don't use them because they massively degrade image quality, 1600x1200 won't pass through these unharmed while on the 8port thing even 2560x1600 didn't show any signs of damage.

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Reply 7 of 22, by kolderman

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I currently use a Lindy 4-port VGA/PS2/audio (powered). It has both buttons and hotkeys, TBH I actually prefer the hotkeys and I don't notice any input lag as a result, I play mainly oldskool FPS. One of the PCs outputs through a DVI->VGA adapter. I also have a near identical ServerLink model which I have not used yet.

Reply 9 of 22, by Tim1075

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In general I prefer using professional equipment. In my setup I use a second hand server console KVM switch (VGA/PS2). They are easy to find on craigslist where I have payed under $30 for a Compaq 8 port model (cables included). For audio mixing I use a mixing desk with multiple inputs so I can manually control the volume levels of each seperate input individually. This is imho the most practical and reliable solution.

Reply 10 of 22, by Roman555

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Tiido wrote:

I have a D-link DKVM-8E and I'm mostly fine with it except that sometimes it forgets that ALT, SHIFT or CTRL was released and you have half messed up keyboard input. This makes games difficult sometimes. Older version of this KVM can do serial mouse to PS/2 translation but I have no clue how effective it is.
I have a few 4 and 2 port ones but I don't use them because they massively degrade image quality, 1600x1200 won't pass through these unharmed while on the 8port thing even 2560x1600 didn't show any signs of damage.

It's interesting because D-link DKVM-8E supports up to 1920x1440 pixel by specifications. BTW the soap double image of 4-port D-Link DKVM-4K I don't like too.

Reply 11 of 22, by torindkflt

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I have a couple different KVMs. Neither of them have audio, but so far I've really not had any need for a KVM with audio.

On my vintage computer desk, I have an old four-port Aten CS-104 that has PS/2 and AT for the keyboard, plus PS/2 and serial for the mouse. I got it from the computer recycling place about 15 years ago. It doesn't combine the PS/2 and serial mouse signals, but it DOES combine the PS/2 and AT keyboard connectors internally, which makes it handy to use my AT Model M keyboard with the newer vintage systems that don't have an AT connector.

On my computer repair workbench, I have a ~2004 Linksys two-port KVM that's purely PS/2 only, someone gave it to me about five years ago. It's kind of annoying to use though, because it is self-powered and has a fairly long delay between when you turn on the computer and when the KVM becomes active, making it unfortunately common to miss short "Press [x] to enter setup" windows. It also seems to randomly mess with the left CTRL key on the keyboard I have connected to it, perhaps because that's part of a keyboard command sequence to switch inputs.

Reply 12 of 22, by feipoa

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Unknown_K wrote:

If you need to switch audio I suggest you use Belkin SOHO KVM switches. I have used them since they made serial port models and still use them today with USB+DVI.

https://www.linuxlookup.com/sites/default/fil … g?itok=xc_gPPXj

Has anyone tested this with Matze79's serial to PS/2 protocal converter? Was there any pointer lag?

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Reply 14 of 22, by SirNickity

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What causes this? Is it just saturating the slower serial port with too many messages from the PS/2 device?

PS/2 is pretty fast -- I'm just now learning how fast it actually is. In theory, you could get a couple hundred reports per second from a mouse. Serial would only support somewhere around 30/sec @ 1200bps. This is all ballpark, assuming 3-byte reports coming in at just under the theoretical bandwidth limit of the interface -- which is probably not realistic, but I don't really know enough yet about device behavior to know what's typical. Given the fairly significant discrepancy, though, it could be that the converter just needs to decimate events before delivering to the serial end.

Reply 15 of 22, by McBierle

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So now i have 4 different switches. Amonghst them the one by Belkin.
I would test them tomorrow, if someone of you would be so kind and babysit my twins 😉
Seriously i'll test them this weekend (i hope).

Reply 16 of 22, by feipoa

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Off topic

Twins - that's lucky. People think its twice the work, but in the long run, it is really only 1.5x more work than 1 kid. Imagine having one child, then three years later having another and doing all the same baby work again. The ultimate stroke of luck is to have fraternal twins - one boy and one girl. Then you're done and time to primary school for all your children is greatly reduced. I have three kids and have been changing dipers straight for 7 hours. They each are at a different developmental stage and catering to this is absolute servitude. I hope the childcare situation is better where you are!

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Reply 17 of 22, by chinny22

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One thing I recommend is getting KVM's that use standard cables.
my no name 4 port KVM is good but uses a serial port connecter on the KVM side so good luck if I losses a cable.
Where as my 8 port Compaq and most enterprise stuff has the vga and 2 ps2 connecters for each input, so you can buy the kvm cables, or just use a standard vga cable and ps2 extension cables.

Audio really limits your options, I just run audio extension cables from the soundcard up to the KVM and manually plug the speakers into whichever I need

Reply 18 of 22, by McBierle

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Ok, i testet those KVMs and decided to stick with this one:

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Those Belkins are just so... unhandy. Obviously no joy with serial mice. I think i'll get a serial switch extra, atm i'm using three mice. 😀

Reply 19 of 22, by Unknown_K

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The older Belkins (PS/2 ports and serial mouse emulation) work great but they don't have audio.

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