ADB Hotswapping

[thekhakinator]

I apologise if this is in the wrong subforum but I couldn't find a better one to post it in. 

Is ADB hotswappable for keyboards and mice? It's just I have something I need to do with 8 Macs at once but I only have 3 keyboards and two mice and so need to swap them from Mac to Mac while they're all on - but I don't want to do any damage. Tips? 

 

[TheWhiteFalcon]

No, don't hotswap. Many people haven't had issues but it is more than possible to blow something out. ADB switches exist but I'm not sure on price and availability.

 

[Trash80toHP_Mini]

No, ADB's not hot swappable per the spec. It's a maybe you can do it without damage, but really should not. That said, mechanical the KVM switches do it, but the rotary switch likely reduces the chance of damage significantly over hot plugging ADB manually.

BTW: Peripherals would be the forum of choice.

 

[uniserver]

I hot plug ADB all the time, never even think twice.

 

[unity]

I too hot swap ADB. But its true, its not really designed for it. And it can cause board damage with most devices out there. So I would never recommend it, especially on these older systems.

 

[uniserver]

when i say that i do it all the time,  most days.  what i mean is i have an AEKII and an ADB mouse plugged into that.  and that is what i hot plug often.  I don't have any other adb devices...   but one thing I can say is I will continue to hot plug with out any worry what so ever...  I have replaced ADB fuses on customers boards before.  Not sure what they were doing but it was enough to blow the fuse.

 

[trag]

ADB is not hot swappable, in theory.   Apple warns (warned) that it could cause logic board damage.   Specifically, causing a change in voltage results in a current which is proportional to the rate of change of the voltage, or vice versa.  So if you rip the plug out fast, you may cause a current (or voltage) spike which will damage ADB circuitry.

In practice, it is rarely a problem, but it can be.

Also, after being swapped, the host system will often only operate the mouse at the lowest cursor speed.  There are ADB Reset utilities which can be run after swapping to get the Control Panel settings to apply properly.

Presumably, KVM switches contain bypass capacitors which will moderate peak currents caused by rapid disconnection/connection.

 

[CC_333]

I think I read somewhere that the ADB protocol, in theory, *can* support hotswapping, but Apple's particular implementation of it does not.

c

 

[TheWhiteFalcon]

LEM claims, with no evidence to back it up, that the Wallstreet does support it.

 

[Schmoburger]

I do it a lot more than I really should...always have. But I try not to make it too much of a habit, because I know Im not meant to. For one, if I pull a keyboard, the cursor speed goes spastic and ends up rather slow.

 

[olePigeon]

I've seen a keyboard and a Kensington Turbo Mouse fry because of hotswapping ADB.  I wouldn't recommend it.

 

[thekhakinator]

Thanks for your responses. It matches a lot of my research thus far - you're not supposed to do it but sometimes it works. I'm either gonna go and buy another 5 keyboards and 6 mice or I'll see if I can figure what aspect of the hotswapping causes problems/damage and maybe I can cobble something together to stop that.

 

[uniserver]

i think its time for some durability testing.    I will sit there for an hour and plug and replug my KBD/mouse...  into an ADB port...   What computer you guys choose.. i have them all on the shelf.

 

[Schmoburger]

Something not particularly rare or well liked... perhaps a 7xxx Powermac as I wont be upset if you blow the ADB circuitry on one of those.

Incidentally, my MacAlly AEK-clone recently died and I beleive it may have been a result of hotplugging in my 9600.

 

[Trash80toHP_Mini]

Apple warns (warned) that it could cause logic board damage.   Specifically, causing a change in voltage results in a current which is proportional to the rate of change of the voltage, or vice versa.  So if you rip the plug out fast, you may cause a current (or voltage) spike which will damage ADB circuitry.

I'd sdd the possibility of mismatched potential levels and ESD. No end of problems generated on that front in the digital world, especially so as the connectors are as directly connected to the ADB controllers as possible. Using a KVM switch keeps all the components involved grounded together. It also ensures that all connections involved are broken and made as close to the same instant as possible.

 

[Unknown_K]

One some models the ADB circuit is fused so you might blow that fuse (better then blowing a chip I guess). Probably depends on the load you are using. One on KVM setup I have an keyboard, ADB tablet, mouse, and trackball connected so the load would be higher then just a keyboard and mouse.

 

[Gorgonops]

i think its time for some durability testing.

I have to admit I'm confused what the point would be. You've said you've replaced ADB fuses for customers before, are you suggesting they blew them some other way besides hot swapping? (Urinating on the port? Probing it with a bent paperclip?) The risk from an individual instance of hot-swapping might be low but clearly the number does come up.

 

[Trash80toHP_Mini]

The risk from an individual instance of hot-swapping might be low but clearly the number does come up.

It's a real number, but is it significant?

Where to draw that particular line seems to be the point. Lightning will strike, but how often will an ADB Mac be fried by it? How does hot-swapping ADB compare statistically?

 

[Gorgonops]

To get reliable statistics I suspect you'd have to repeat the experiment literally thousands of times across a representative sample of ADB hardware (not just one random Mac model that may be more or less susceptible than average) and also explore a range of auxiliary variables as well. (For instance, does the angle of the plug as it's inserted, thereby changing which wires make contact first, make a difference?)

The one thing we do know WITHOUT experimentation is if you don't hot-swap you won't blow out your port from hot-swapping.