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KVM hacks
- Thread starter Bunsen
- Start date
My guess is that it will not work. The video should be ok but ADB is a serial chaining protocol that is way different from PS/2 mouse and keyboard ports.
I tried it a few years back but could not get it to work with PS/2 and bought an ABD KVM box (Dr. Bott).
I was using an ADB to PS/2 converted that worked ok stand alone but when plugged into a KVM switch it would hang.
I tried it a few years back but could not get it to work with PS/2 and bought an ABD KVM box (Dr. Bott).
I was using an ADB to PS/2 converted that worked ok stand alone but when plugged into a KVM switch it would hang.
Most smart KVMs isolate the input PS/2 from the outputs and emulate a PS/2 keyboard to stop the machine at the other end freaking out. You could probably do it on an old-fashioned hard-switched one but then you'd risk all sorts of nastiness with shorts etc., there's a good reason they stopped being popular for anything other than switching printers 
PS/2 has been surviving on the tail of the dog for too many years. During the survival years, I have wasted too much time at work trying to find KVMs that work with different PCs. Tacking on PS/2 support to modern chipsets is a ridiculous concept that causes pain. SJ was right when introducing the iMac with no legacy ports. If you need to use a legacy device, buy a USB adapter, and let the manufacturer provide customer support.
Legacy hardware support costs us all. Cheap KVMs use PS/2 and VGA which are 20 year old technologies. If Intel, Dell, HP and others had pursued the non-legacy route that they promised seven years ago, the world would be different.
Legacy hardware support costs us all. Cheap KVMs use PS/2 and VGA which are 20 year old technologies. If Intel, Dell, HP and others had pursued the non-legacy route that they promised seven years ago, the world would be different.
LOL, yes my brother is getting ready to switch from the PC world to that of the Mac. He was reading the specs of the MacBook Pro and was concerned because it did not have a keyboard port for an external keyboard like his Dell laptop and wanted to know if I would recommend getting a USB keyboard. I had no idea the PC world was so far behind the cutting edge of technology.
Some people don't want to plop down good money to have a USB keyboard instead of a PS/2 keyboard, I just need a keyboard that is cheap and that works, I cannot find a USB keyboard in my area that fits those requirements. Plus it frees up a USB port! I just cleaned the dirty USB keyboard that my friend gave me with his iMac, if it were a PS/2 keyboard I would of just got a new keyboard. Need to order a PS/2 to USB adapter from dealextreme.com.
Well, I for one prefer PS/2 keyboards to USB. I still use PC-DOS (all my Windows computers dual boot DOS) and a lot of motherboards do not provide USB keyboard emulation of PS/2 ports in the BIOS. DOS USB drivers are scarce, $$, and take up memory.
It's kind of hard to run DOS without a keyboard. [
] ]'>
It's kind of hard to run DOS without a keyboard. [
] ]'>
You'd still not totally eliminate the chance of a jump as the switch sat between 2 contacts I don't think. The I've had nasty arcing noises out of video switches when the switch jammed between 2 poles before now - a bit unnerving. Remember ADB has a voltage running down 2 wires...
For video, hardware switches also tend to screw up your video signal as they aren't usually very well shielded and all the signal wires are split up and fed around the box individually (at least on the cheap ones I have).
There are two concerns with ADB switching:
1. Performing a clean flip. However if you use the internals from an S-Video switch box (or even a hacked PS/2 box) this should work.
2. ADB device awareness. ADB detects devices on startup and doesn't like hot swapping. There is a utility that resets the ADB bus (name, anyone?) that normally fixes it.
For my 9600 (that I thought was an 8600 because I read the badge on the front of the case), I use one of Belkin's ADB adapters with a conventional Belkin VGA/PS/2 KVM. UK keyboard mapping is all over the place, but it works more or less. (This is not a general recommendation for Belkin KVMs. I've used a few that were very unreliable. For a conventional VGA/PS/2 KVM, I suggest Linksys.)
1. Performing a clean flip. However if you use the internals from an S-Video switch box (or even a hacked PS/2 box) this should work.
2. ADB device awareness. ADB detects devices on startup and doesn't like hot swapping. There is a utility that resets the ADB bus (name, anyone?) that normally fixes it.
For my 9600 (that I thought was an 8600 because I read the badge on the front of the case), I use one of Belkin's ADB adapters with a conventional Belkin VGA/PS/2 KVM. UK keyboard mapping is all over the place, but it works more or less. (This is not a general recommendation for Belkin KVMs. I've used a few that were very unreliable. For a conventional VGA/PS/2 KVM, I suggest Linksys.)
I've hot-plugged ADB keyboards and mice after boot (mostly when the wire fell out or I forgot to plug them in) on numerous occasions and had them work fine. I know you aren't supposed to, but sometimes... well I can't be bothered to do anything else. [] ]'>
I use Belkin PS/2 adapters on my Suns and they work pretty well. I wouldn't use one of their KVMs if you paid me thogh, they are pretty aweful in general. I tend to sway for enterprise KVMs, either HP/Compaqs or Avocent (I think my Compaq is actually an Avocent inside the box). I have a little self-powered 4-port KVM I take to meetings and stuff, but it's a bit more fussy about older signals than the big KVM I use regularly.
If you want a good 8-port PS/2 KVM I recommend you look up the Compaq one, BUT make sure you get a later one with the coloured port stickers on the back. The early ones are much more basic and fussy about video signals (SoG for example will crash my older black ports Compaq one I used to use). The OSD on the Compaqs is very cool, on my current one it even has a mouse pointer and draggable window. It is a 'smart' KVM though however, and so it mashes up inputs and outputs, it'd be no good for hacking to use with ADB. I dread to think what it cost new [] ]'>
] ]'>I use Belkin PS/2 adapters on my Suns and they work pretty well. I wouldn't use one of their KVMs if you paid me thogh, they are pretty aweful in general. I tend to sway for enterprise KVMs, either HP/Compaqs or Avocent (I think my Compaq is actually an Avocent inside the box). I have a little self-powered 4-port KVM I take to meetings and stuff, but it's a bit more fussy about older signals than the big KVM I use regularly.
If you want a good 8-port PS/2 KVM I recommend you look up the Compaq one, BUT make sure you get a later one with the coloured port stickers on the back. The early ones are much more basic and fussy about video signals (SoG for example will crash my older black ports Compaq one I used to use). The OSD on the Compaqs is very cool, on my current one it even has a mouse pointer and draggable window. It is a 'smart' KVM though however, and so it mashes up inputs and outputs, it'd be no good for hacking to use with ADB. I dread to think what it cost new [
] ]'>
For this given Problem to share peripherals between two ADB equipped Macs, consider to include use of the software Remote Mouse and Keys. In short, you can share the Keyboard and Mouse input from one Mac via AppleTalk network connection with a second Mac. To trigger this software KM switch you just »leave« the screen with the mouse pointer through a corner at the menu bar. Magically, further input applies to the other machine until you leave its screen back into the first one, which is physically connected. The hassle of repeated ADB resets is completely removed and only a switching device for the video output would be left to make it work as a complete KVM solution. Any manual VGA switch with mac monitor adapters will do.
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