Is it safe to use both ADB ports on a keyboard?

[protocol7]

My 5400 only has one ADB port on the back and I want to attach a ADB gamepad. Until now I did this by disconnecting the mouse from the keyboard, but as the keyboard on my Classic II has two ADB ports (apparently so you could attach the mouse for left or right-handed use) I was wondering if I could use it instead and have the mouse and gamepad attached to either port.

I just want to be sure there's no danger of overloading or frying anything before I try this

 

[Bunsen]

Perfectly safe- that's what they are there for.

 

[BarnacleGrim]

I read somewhere that you should absolutely not plug or unplug anything while the computer is on, but that might have been serial or SCSI. Still don't know why they said that either.

Were there ever made ADB hubs? The AppleDesign keyboard only has one port, and I haven't since seen a Mac with two ADB ports either.

 

[Gorgonops]

Apple says that hotplugging ADB is a bad idea. Most Macs lack any isolation on the ADB input pins and the transient you get from yanking a device *could* in theory kill it. (And if you google you'll find it happens in practice as well.)

They did and still do sell ADB splitters. $3.70 isn't much to pay to avoid wrecking a motherboard.

 

[Anonymous Freak]

The main reason for not hot-plugging or hot-unplugging devices are improper grounding. Plugging or unplugging can generate a small surge, which, in modern hot-swap connectors is mitigated by having the ground pins longer than the others, allowing any surges to harmlessly dissipate through ground.

That is the main reason not to plug/unplug ADB or serial.

SCSI, on the other hand, has a whole other set of issues. It is actively sending data back and forth all the time, and only initializes the bus on boot. If you plug or unplug something while the system is running, it will mess up the communication between *ALL* devices, and very likely crash the OS.

 

[Dog Cow]

from yanking a device *could* in theory kill it. (And if you google you'll find it happens in practice as well.)

No, you don't have to go far. I have a Mac LC whose ADB ports are dead because I accidentally hot-plugged them.
AFAIK, these are the ports not to mess around with:

- ADB

- SCSI

- power ( )

- floppy disk

Again, AFAIK, these ports can be hot-plugged:

- video

- serial

Knowledge for the above list has come from personal experience, hear-say, and reading the Apple manuals.

 

[mac2geezer]

And as a trivial addition, Ethernet (RJ45) cables can be plugged/unplugged at will; at least in my experience.

 

[Scott Baret]

I second the Ethernet/RJ45 unplugging. If you've ever had the privilege of working in a patch cord room you've probably experienced this.

I'm curious about your keyboard. Most Apple keyboards don't have two accessible ADB ports. True, there is one on either end, but one side is usually used for the Mac-->Keyboard cable. I know the original ADB, original extended, Apple Keyboard II, Apple Extended Keyboard II, and IIGS keyboard are like this. AppleDesigns only have one ADB port on the underside but use a built-in cable to connect to the Mac.

 

[protocol7]

I've been a bit busy since so I only took a proper look at the keyboard today and Scott's right, one port is for the keyboard cable itself. So I'll need to get one of those splitter cables Gorgonops mentioned earlier (assuming they don't charge me 5x the price just for shipping).

As for the hot-plugging I heard the same thing years ago with PCs too. I think it was with keyboards and mice, but probably related to anything serial as well. There was a risk it could short out something.

 

[BarnacleGrim]

My adjustable keyboard is very flaky, also using the mouse through it. ADB hotplugging damage? It's tempting to hotplug when troubleshooting.

Didn't Kensington make a product for...eh...lukewarm-plugging serial devices? With everything grounded there shouldn't be any risk.

'

I guess re-initing the SCSI bus while running would be impossible because that would disconnect the boot disk, but if the boot disk was ATA?

 

[protocol7]

I found a page listing a ADB/S-Video splitter. Are ADB and S-Video both wired the same way? I might have better luck finding a S-Video Y-cable locally than a ADB one.

 

[Bunsen]

You sure your gamepad doesn't have a piggyback connector on the ADB plug? Some did.

I've hot-swapped SCSI drives without crashing the OS, sort of...

• Unmount from desktop (with SCSIProbe etc)
  
• Pull power connector from drive
  
• Let spin down
  
• THEN pull SCSI connector.

To mount a drive, do all steps in reverse.

NB, never tried this under OS X or on a SCSI card.

 

[protocol7]

Nah there's no piggyback port (though I can see why there would have been a need for one) but I think I can manage ok now without a splitter. The main problem I had when I first got the pad was with the position of the ADB port on the AppleDesign keyboard. However with the Apple Keyboard II the ADB ports are right there on the sides. I can use the trackball on the pad in place of the mouse so it's all good.

Still curious to know about the ADB/S-Video compatibility. I read that it depends on grounding, but I don't know how you'd be able to determine this if purchasing one.