Plug-and-Play, or PnP, is a
specification built into newer systems so that you can install devices
built for it with minimal hassle. All of the settings, like IRQ’s and
drivers, are taken care of so that, theoretically, you can have your
new hardware working for you in a couple minutes.
The Macintosh had PnP before the PC
did. It wasn’t till 1993 until it began to take part in the PC world.
Four companies took part in this promotion: Microsoft promised a new
OS that could take advantage of PnP, Intel promised PnP chips, Phoenix
promised the BIOS, and Compaq decided to build the computer. It was
realized that PnP could be a real money maker. Installation and
configuration could be a real breeze. There would be fewer calls to
tech support, and hopefully, people would buy more parts because they
weren’t daunted by the chore of putting it in.
In an ideal world, when you plug in a
PnP device, Windows 95 will detect the new hardware, adjust the
settings, and install the drivers. Many call it "Plug and
Pray", though, because it is rather moody, but the technology has
improved greatly, and most installations are hassle free.
Not all systems can handle PnP. You
must have a PnP operating system, such as Windows 95/98. Previous
versions of Windows can’t do it. Your hardware must be rated for PnP.
This means that the system bus must be capable of PnP. The PCI bus was
designed with this in mind, and most boards have the ISA slots PnP
capable as well by linking them to the same circuitry. You need 32-bit
drivers for the device…not to worry though…they come with it. Your
peripherals must be PnP compliments, meaning they must be able to
accept the settings given to it by the OS as well as have the ability
to identify itself to the OS when asked. And lastly, your BIOS must be
compliant with PnP.
All of these are easy to get, except
BIOS. If your system does not already have PnP BIOS, you will need to
replace your BIOS, or just upgrade to a new motherboard. All newer
computers, say 1995 or later, have PnP BIOS in there already.
How It Works
A PnP system scans the entire system
for new hardware every time the system is booted. It also determines
what every device needs, and makes sure it gets it.
It scans for legacy devices,
or non PnP devices. These devices can’t change their settings and have
fixed requirements, so the system must first find these, then
configure the other PnP devices around it. Although Win95/98 can’t
automatically adjust a legacy’s settings, it can often recognize it
during install. Win95/98 has many legacy device drivers built into it.
Old hardware will work under 95. If it will work under Win3.x, it will
work with 95.
Let’s walk through the boot process
of a PnP computer:
Create a table of available resources, including IRQ’s, DMA’s, and
I/O addresses, but not including those required by system devices.
2) Search the system and determine which are PnP and which
are not. Identify each peripheral.
3) Load the last-used ESCD, or Extended System Configuration
4) Compare this ESCD with the current configuration. If
identical, continue with normal boot. If not, go to step 5.
5) Reconfigure the ESCD. Scan the resource table created in
Step 1, ignore those settings being used by legacy devices, and
assign the remaining resources to the PnP devices.
6) Save the new ESCD, and print message to screen stating:
7) Continue with normal boot process.
Very simply…plug-and-play doesn’t
always work. Whether you have all PnP hardware or a mixture of PnP and
legacy devices, PnP can be rather hit and miss.
One common cause for problems is that
the system is attempting to assign settings taken by a legacy device to
a PnP device. A PnP system has no adjusting abilities when it comes to
a legacy. The more legacy devices you have, then, the more problems
you will have with PnP.
Another reason is due to the broad
array of systems out there. Every system is different, with old
drivers, old BIOS, off-brand hardware, you name it. There is no way
manufacturer’s can design hardware for every possibility.
Installers of new devices, though,
sometimes find themselves fighting the plug-n-play on their
system. PnP is reasonably good at handling simple conflicts, but, is
not nearly as resourceful as a human being at thinking through things.
PnP simply can’t sit there and figure out some clever way to get
everything to work without conflicting. Moreover, PnP can be very
stubborn. Sometimes, it seems the PC is bent on assigning your new
modem to COM 4, IRQ 3, which will conflict with the serial port,
despite your best efforts to assign it to COM 3, IRQ whatever. For
this reason, some feel the need to slam their computer upside the case
with a baseball bat! Trust me, it happens. =)
The good news is that PnP problems
are on the decline as companies iron out problems as they learn. PnP
hardware is getting more and more user-friendly.
Sometimes Windows just won’t detect
your new hardware when you boot it up. In this case, you just have to
tell it to look for it. You do this in Add New Hardware Wizard in the
Control Panel of Win95/98.
Just follow the on-screen
instructions. When it asked you if it can scan for new hardware,
select yes (recommended). It will tell you that it might take a few
minutes. Fine. Click next. It will search. If it finds it, it’ll
display it in a box. If it correctly identified the hardware, click
Finish, and it will install the drivers or ask for a disk. If it can’t
find it, it will ask you to manually install it. Click Next. It will
give you a big list of devices. Try to find yours on the list, select
it, and click Finish. If it’s not there, and you have a disk with the
software on it, click Have Disk, and do it that way.
Again, the Wizard can try to do some
strange things at times. Such is the nature of PnP. To avoid trouble,
use the nifty "Have Disk" button whenever you do have the
disk. Sometimes, the wizard can properly do things and install some
Win95/98 stock drivers, but the manufacturer drivers are the best.
In order to avoid trouble, it is best
to make sure that all PnP hardware that you buy has a manual override
on it, so that it has legacy capability. The best ones have a set of
jumpers. The jumpers are factory set to the PnP setting. But, if you
move the jumper bridges, you take it out of PnP mode, and it turns
into a legacy. Follow the jumper diagram in the manual to adjust
settings manually. Sometimes, you can manually install a new device in
this way in case PnP just refuses to detect it for you.
Also, go into your Device Manager
every once in a while and delete old, unused drivers. When you install
new hardware and replace old stuff, Win95 has a habit of leaving the
old drivers there, and slow the system down. Make sure you don’t
delete the CD-ROM drivers or mouse drivers.
Also, it is best to buy PnP hardware
from major manufacturers. Keep the drivers up-to-date.
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