New Product: KeyWiz-QD™ - GroovyGameGear

[diverdown]

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I'm looking into some sort of wiring product to go along with this.  Not sure what form it's going to take at the moment though.

RandyT
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Just 1 word


Bloody Fantastic

[Tiger-Heli]

To clarify, I have had problems hot-swapping PS/2 mice, not keyboards.

[Guaranos]

Yeah - I've seen computers lock up when "hot-swapping" a ps/2 port. Does stop me from still doing it on work computers - usually it's fine...

In some cases it can do worse than cause a lock up.  It's rare, but it can cause you to short out your keyboard or mouse port.  I've only seen that once or twice in many years working with PC hardware.

As for the DB-25 M/F cables, I just threw out a big stack of them a couple of weeks ago (along with M/M and F/F cables) since I no longer own any devices that use them.  Now that I think of it, my computer that I use daily doesn't even have a parallel port on it...

[RandyT]

In some cases it can do worse than cause a lock up.  It's rare, but it can cause you to short out your keyboard or mouse port.  I've only seen that once or twice in many years working with PC hardware.

I've never seen one "lock up" when the keyboard is swapped out, but anything is possible I suppose.  Hot swapping the PS/2 mouse port can be more troublesome.

Also, the port does not "short out".  In the old days, keyboards were big, and power hungry.  Lots of discrete hardware, mechanical switches and so on.  The port wasn't originally designed for hot swapping, so on very old motherboards (we're talking 486 / Pentium 1 era and before) they had only a small fuse to protect the rest of the system from a short circuit in the keyboard.  The ancient keyboards also had nothing that would ramp the power to prevent a surge from popping the fuse, and that is what caused the problem.  BTW, those old motherboards weren't dead, they just didn't have 5v going to the PS/2 port anymore.  A quick splice of the 5v supply into a short PS/2 extension cable and you were back in business.

Fast forward to today.  The power and data lines on  modern motherboards often go to the very same places as those connected to the USB ports.  Quite a while back, more devices started using the PS/2 port for an external power tap, so more robust power handling was built into the circuitry.  Self resetting breakers have become inexpensive and have pretty much taken the place of the fuses.  Modern keyboards (and the KeyWiz) draw very little power compared to the old beasties, and have components to rapidly ramp up the power rather than creating surges when they are plugged into the ports.

We have sold thousands of PS/2 Keywiz's and to date have had zero reports of someone damaging their system through a hot-swap.  I'm not saying it can't happen, but the numbers indicate that you might have a better chance of being struck by lightning

RandyT

[Guaranos]

Also, the port does not "short out".  In the old days, keyboards were big, and power hungry.  Lots of discrete hardware, mechanical switches and so on.  The port wasn't originally designed for hot swapping, so on very old motherboards (we're talking 486 / Pentium 1 era and before) they had only a small fuse to protect the rest of the system from a short circuit in the keyboard.  The ancient keyboards also had nothing that would ramp the power to prevent a surge from popping the fuse, and that is what caused the problem.  BTW, those old motherboards weren't dead, they just didn't have 5v going to the PS/2 port anymore.  A quick splice of the 5v supply into a short PS/2 extension cable and you were back in business.

I know that it was usually the fuse popping, and not technically the port shorting out, but you can also fry the microcontroller that controls the port itself.  I was avoiding making the distinction to save some people's eyes from glazing over, since most people, even some in a technically proficient group like this one, will probably just consider the port "dead."

From the wikipedia article on PS/2 connectors:

"PS/2 ports are designed to connect the digital I/O lines of the microcontroller in the external device directly to the digital lines of the microcontroller on the motherboard. They are not designed to be hot swappable. Hot swapping PS/2 devices usually does not cause damage due to the fact that more modern microcontrollers tend to have more robust I/O lines built into them which are harder to damage; however, hot swapping can still potentially cause damage. Shorting one pin to another on a PS/2 port can easily kill one or both microcontrollers."

The full article:  http://en.wikipedia.org/wiki/PS/2_connector

[RandyT]

I know that it was usually the fuse popping, and not technically the port shorting out, but you can also fry the microcontroller that controls the port itself.  I was avoiding making the distinction to save some people's eyes from glazing over, since most people, even some in a technically proficient group like this one, will probably just consider the port "dead."

From the wikipedia article on PS/2 connectors:

"PS/2 ports are designed to connect the digital I/O lines of the microcontroller in the external device directly to the digital lines of the microcontroller on the motherboard. They are not designed to be hot swappable. Hot swapping PS/2 devices usually does not cause damage due to the fact that more modern microcontrollers tend to have more robust I/O lines built into them which are harder to damage; however, hot swapping can still potentially cause damage. Shorting one pin to another on a PS/2 port can easily kill one or both microcontrollers."

The full article:  http://en.wikipedia.org/wiki/PS/2_connector

But as with most wiki entries, it's not entirely correct and it doesn't tell the whole story.  For instance, shorting one pin to another is impossible unless you physically damage the connector.  And, unless it's the wrong two pins, namely GROUND and +5v, you still have little to worry about except the broken connector.  It also states that "modern microcontrollers have more robust I/O lines that can handle this, yet somehow they can still be damaged ?!?  How?  Who wrote this and what is their background? 

It also goes on to give an example of swapping out a USB mouse for a PS/2 mouse and then the PS/2 mouse won't work.  This is related to an OS issue and has nothing to do with the physical properties of the PS/2 port.  If the driver wasn't started at boot time, the PS/2 mouse won't have a chance of working.  But PS/2 mice and PS/2 keyboard devices are different birds anyway.

I am probably one of the few individuals who can say that they have hot-swapped the PS/2 port on the same system many thousands of times.  Every KeyWiz interface is tested, by myself,  100% for functionality before it is shipped, on my trusty old emachines P2.  I never turn the machine off to do this and it's still functioning as happily as when it was built so many years ago.  With this number of practical, real world hot-swaps, "luck" doesn't enter into the picture.

The nice thing about wikis is that you can fix them (and I did)

RandyT

[Tiger-Heli]

I'm probably only in the hundreds of swap times, but never a problem here either.

[patrickl]

I did blow a PS/2 port once.

[bleargh]

Can't say I've ever blown a PS/2 port, but I've seen several Dell servers that'd lock up entirely if you hotplugged the keyboard.  I, uh, even have a few of them...

[RandyT]

I did blow a PS/2 port once.

How?  (and I'll refrain from the obvious puns.... )

[shorthair]

I've never had trouble with USB devices...I take that back...in some cases, some ports don't seem to like something like an external hard drive...but they always recognise the device in some way. PS/2's, though, I thought it was standard that they just wouldn't recognise if you plugged them in after boot. That's always been my experience. No troubles, either.

[RandyT]

PS/2's, though, I thought it was standard that they just wouldn't recognise if you plugged them in after boot. That's always been my experience. No troubles, either.

Plugging in after boot, and hot-swapping are two different issues.  If you plug in after boot, especially with post 98SE OS's, there's a good chance that the system will not have loaded any drivers to support the devices.  However, if a standard 101-key keyboard driver was loaded as a result of the keyboard being plugged in at boot time, then swapping another standard keyboard device after boot will have a much higher likelihood of success.

I have to say here, however, that this subject really doesn't apply to the product that is the topic of this thread.  This unit swaps controls via the DB-25 connections, not the PS/2 port.  There is no pass-through on this unit as it was designed to work alongside of a system with a USB keyboard attached, or in the case of a dedicated cabinet, by remote management.  USB keyboards are very cheap nowadays and a better solution than bogging down and adding expense to your input controller with a pass-through.

But if you want to hot swap it, and your system is PII class or better, then give it a shot.  If it works on your system, then great.  If not, then leave it attached, build your panel around the DB-25 connectors and use a USB keyboard.

RandyT

[Zebidee]

I once fried an ipac hot-swapping from PS2, and my brother once fried his mainboard doing it with a keyboard.

You can do it a thousand times with no problem.  It that 1001-th time that is the killer.

[RandyT]

I once fried an ipac hot-swapping from PS2.....

Are you sure it died from the swap and not a static discharge to one of the pins in the connector when you picked it up?  That's a much more likely cause in that scenario.  The lines  going to the chip are the exact same ones used in USB mode, and it's only a different part of the firmware that gets executed.

You can do it a thousand times with no problem.  It that 1001-th time that is the killer.

Yeah, kind of like driving to work, walking down a public street at night, or playing contact sports.

FWIW, I have popped a keyboard fuse in my past as well.  But it was a P1 class Cyrix system, a big steel IBM clicky keyboard, it was a long time ago, and it pretty much did it on the second time I tried it.  I also fixed it in about 15 minutes using the method described above.

This discussion is nearing being tantamount to people not going swimming in a pond, because their grandfather did when he was 4 and contracted polio from it.  The early implementations were specced at providing up to 100ma through the port, so you can bet that the fuse they used was just a fraction over that (no hot-plug, so no significant overrating to account for current surges on the 5v line)  The last PS/2 port fuse I looked at, which was on my "bottom of the barrel", 6+ year old emachines motherboard, was a self-resetting type rated at 3amps!  That's 30 times more current than the port was originally specified to handle, and it doesn't fry.  It acts like a thermal switch that opens when it gets hot and closes automatically when it cools off.  The only real challenge is knowing just when they started building them better, so some caution may still be in order on old motherboards.

And just for fun, I have to share a moment of my own stupidity.  I have a system in front of me that I develop on that has some cheap, side panel USB ports.  I had the plug turned around the wrong way (I was working blind from the other side of the machine) and I attempted to put it in the socket. It didn't go, but it allowed enough of it to go in to short the connections.  I now have two dead USB connections on that machine. Theoretically, that probably shouldn't have happened, but individual implementations will vary and therefore always allow for the occasional anomaly.

RandyT

[Zebidee]

I once fried an ipac hot-swapping from PS2.....

Are you sure it died from the swap and not a static discharge to one of the pins in the connector when you picked it up? 

Well, only [insert deity of your choice] knows for sure.     But I am careful with my equipment, so you shouldn't be quick to jump to that conclusion.  I noticed that my IPAC was dead right after I had hot-swapped it from PS2.  I had hotswapped the same IPAC on USB a zillion times before (well, maybe not that many,  but a lot).  So go figure. 

Regarding your discussion about mainboards, it was about 10 years ago that my bro blew his hotswapping a PS2 keyboard.  So it was an older type.

I don't like to talk in certainties, but I thnk the prudent person should turn off the PC before plugging in a PS2 again.  I mean, you can theorise about it if you like but I look at it like this:  If if barks, has fur, and enjoys playing fetch with balls then it is fair to assume that it is a dog.

But it could still turn out to be a seal ....