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non plug and play device on com port?
Question.
Charles Brooks' A+ cert book says the following in chapter 8: "To install a non PnP device on a specific COM port (that is, COM2), you must first disable that port in the system's CMOS settings in order to avoid a device conflict. If not, the system might try to allocate that resource to some other device because it has no way of knwing that the non PnP device requires it." If the BIOS won't know to automatically allocate resources to a device unless it's PnP, how does the device ever get recognized? I don't understand why disabling a comport is gonna help you get the system to allocate resources to a non-PnP device. And are we talking about the BIOS or the OS? Is he implying that I should disable the port in the CMOS, plug in the device, install the Windows drivers, then re-enable the port in CMOS? If so, why would that help? David |
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On Sat, 19 Jul 2003 09:45:46 -0700, David K wrote::
Question. Charles Brooks' A+ cert book says the following in chapter 8: "To install a non PnP device on a specific COM port (that is, COM2), you must first disable that port in the system's CMOS settings in order to avoid a device conflict. If not, the system might try to allocate that resource to some other device because it has no way of knwing that the non PnP device requires it." If the BIOS won't know to automatically allocate resources to a device unless it's PnP, how does the device ever get recognized? I don't understand why disabling a comport is gonna help you get the system to allocate resources to a non-PnP device. And are we talking about the BIOS or the OS? Certain devices have traditional resources associated with it. Since you're using COM ports, I'll use a modem example so we're on the same page. On a typical motherboard, COM 1 and COM2 are associated with the onboard serial ports, and with specific port addresses and IRQs. You can change this, but usually these built-in ports aren't PNP, you have to change the port settings with these connectors manually in the CMOS. Not a big deal with a PNP modem, since the PNP OS would simply notice the potential conflict and keep trying its list of resource options until it hits a combination that doesn't conflict. The problem with a non-PNP modem is that since the resources it needs are set in hardware (typically by dip switches or jumpers), the OS can't just move the modem to different resources. It has to be THOSE resources BUT those resources are already in use and have an owner -- The onboard serial ports. So, you get a conflict, which can result in the system not booting, the system hanging when you try to use one of them, or simply that neither device is available for use. You have to choose which one you want to keep active since you can't share resources unless the devices involved are able to do this. Not many PC devices are capable of this, and those that are, don't always do so successfully. This is why it's customary to disable a COM port in the CMOS. Is he implying that I should disable the port in the CMOS, plug in the device, install the Windows drivers, then re-enable the port in CMOS? If so, why would that help? No. Keep the port dead, or if the motherboard allows it, manually remap the port so that you don't have any conflicts. Since the non-PNP modem is an immoveable object, you can avoid the conflict by removing one conflict source (the serial port) or reroute it (if possible) so that it steers clear of the modem's resources. Not too difficult, just imagine two stubborn kids in a playground who don't get along. Your options for peace are remove both kids, remove one kid, or try to keep kid A away from kid B. Having them shake hands and be friends isn't always an option. David ---------------------------------------- Thanks, MCheu |
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