Charlie Ruggiero
- 2001.02.28
Q: Recently I read about how FireWire and USB on newer Macs are
hot swappable (this means you can unplug and re-plug devices while
the computer is on). I am confused, because I thought that serial
and ADB connections on older Macs were hot swappable as well. I
have swapped out both connections without problems.
A: This, as I remember, was a hotly debated subject between
various experts in the field. When it all comes down to it, there
is not a clear cut answer for all the older connections.
Serial (modem and printer ports) on older Macs is
considered by most (including me) to be hot swappable. I have
swapped thousands of serial devices with no problems I could
detect. To be careful, you should always do what Apple says. As a
general rule, you should only swap devices when they are not being
accessed. You can cause problems with FireWire and
USB if you unplug them while data is being transferred.
Serial is the same way: If you are transferring data via local talk
or through a modem unplugging the device or cable could cause data
corruption. I would not expect this to cause hardware damage,
however.
ADB in my opinion, is not hot swappable. I have seen many
people swap keyboards and mice with no problems, but I have also
seen the ADB port become dead because of this very same thing.
Although rare, hardware damage can occur to both your computer's
port and the devices you plug in. It is best to shut down your
computer before swapping any kind of ADB devices. After all, data
corruption is far less serious than hardware damage (especially if
you back up your data frequently).
- Update: ADB is hot swappable on the PowerBook G3 Series (WallStreet).
SCSI (not considering some advanced server SCSI
solutions) is not hot swappable. You can cause serious damage to
hardware and data by unplugging and re-plugging SCSI cables and
devices.
Headphone/Speaker Jack is hot swappable to a point. I say
this because a lot of people use speakers. Be sure to turn your
speakers down or off before you plug them into this port. When the
metal touches the back it could cause a pop, which, if the speakers
are turned up enough, can break the speakers.
Monitor port is sometimes considered to not be hot
swappable, but I have never seen damage from someone plugging in a
monitor after the computer has started up. If I do unplug or plug
in a monitor after the computer is on I always make sure the
monitor is off before doing so. If you want to be on the safe side,
shut down your computer before unplugging your monitor cable.
Sometimes when you plug in a monitor after you turn on the
computer, you will not be able to set a resolution above the
default. To fix this, just restart with the cable already in.
Floppy port (like on the Mac Plus) is not hot
swappable.
Ethernet (this includes the various different connection
types) is always hot swappable. If it was not, then every time your
computer lost a network connection there could be damage.
Modem connections are the same as Ethernet.
S-Video in/out and composite (RCA) video in/out
are hot swappable. These connections are similar to those you would
find on your VCR and DVD players.
The bottom line is that you do not know always shut down and do
your cable swapping. Incorrect use of hardware is not covered by
your warranty, so always follow Apple's recommendation (which you
can find either in your manual or in their vast tech-info
archives).
Charlie Ruggiero has used a lot of Macs, from Plus to G4, and
even ran a BBS (remember those?) on a Plus. He works as Macintosh
tech support and technology advisor for the College of Education at
Michigan State University. He does a lot of hardware and software
troubleshooting, as well as a great deal of video editing, capture,
and streaming. Charlie is well versed in HyperCard, fairly
knowledgeable in Future Basic, and has a good background in sound
and video. He even has his own site, Edge of Heaven.
