Thread
ADB Hotswapping
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?
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?
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.
BTW: Peripherals would be the forum of choice.
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.
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.
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.
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.
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.
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.
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.
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.
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.
] ]'>Then there's FireWire... Supposed to be hot pluggable, but easy for careless people to fry things. I remember countless DV camcorders with fried FireWire ports and a few that were completely dead from students and staff misaligning the 6 pin plug when connecting to the computer's powered port. The cameras all had a 4 pin unpowered connection, so it seems there was no protection there. The user would invert the plug when connecting to the computer, powering the data lines on the device. On eMacs and iBooks, it would kill the FireWire port on the computer rather than the camera, blowing a fuse that could be desoldered and replaced. The ubiquitous iMac G3 slot loaders would wreck the cameras. We tried to institute a policy of connecting the cable to the computer first to avoid the mismatch, but... I ended up having to solve the problem by hot gluing cables to computers. Sometimes behaviour has to be modified by the environment.
If we want specifics.
I have only changed (2) ADB fuses and they were physically blown, as in you could see it.
And they were the earlier Revision SE/30... The shape was round yellow and disk like.. about the size of a dime.
Other wise I haven't had to change any of the other style of fuses.
and have never had to change an ADB controller.
and never had ADB issues with any MB other then with that specific SE/30 RevA's, and that round
disk like fuse they used for a short period of time.
I have re-capped so many boards its just obscene. I wouldn't lie just to prove a point.
Its just fact that i am absolutely correct.
Hot plugging ADB does absolutely nothing to harm your main board other then maybe slow your mouse speed down when you plug it back into the original machine. Witch gets fixed with a reboot.
I have only changed (2) ADB fuses and they were physically blown, as in you could see it.
And they were the earlier Revision SE/30... The shape was round yellow and disk like.. about the size of a dime.
Other wise I haven't had to change any of the other style of fuses.
and have never had to change an ADB controller.
and never had ADB issues with any MB other then with that specific SE/30 RevA's, and that round
disk like fuse they used for a short period of time.
I have re-capped so many boards its just obscene. I wouldn't lie just to prove a point.
Its just fact that i am absolutely correct.
Hot plugging ADB does absolutely nothing to harm your main board other then maybe slow your mouse speed down when you plug it back into the original machine. Witch gets fixed with a reboot.
I think we have to look at it this way. Has anyone blown an ADB device or ADB connection on a logic board by swapping with a system that is powered down?
If the answer is "no", and we have at least anecdotal evidence that it has happened when people tried to hot-swap, we have to accept that hot-swapping does indeed carry some risk above that seen with swapping cords while system is off.
If the answer is "no", and we have at least anecdotal evidence that it has happened when people tried to hot-swap, we have to accept that hot-swapping does indeed carry some risk above that seen with swapping cords while system is off.
I have no qualms about hotswapping ADB. at a MUG event ten years ago, a veteran AASP shop owner compared it to speeding:
"You're not supposed to do it, but pretty much everybody does. The difference is that the Mac probably won't crash."
The only ADB failures he could recall were related to S-VHS/S-Video equipment being connected to the ADB chain.
If I cause damage to a machine by my own actions, I'll admit my stupidity and take responsibility. I take no responsibility if someone else takes this as advice and causes a catastrophic cascading global telecommunications and power grid failure by hot plugging ADB to a toaster.
"You're not supposed to do it, but pretty much everybody does. The difference is that the Mac probably won't crash."
The only ADB failures he could recall were related to S-VHS/S-Video equipment being connected to the ADB chain.
If I cause damage to a machine by my own actions, I'll admit my stupidity and take responsibility. I take no responsibility if someone else takes this as advice and causes a catastrophic cascading global telecommunications and power grid failure by hot plugging ADB to a toaster.
Here's a link to an ADB 4 way switch currently available on eBay. http://www.ebay.com.au/ulk/itm/252153542078
)] ]'>