Plug-n-Play efforts

Question: I have a Pentium 100 MHz with 16 megs of EDO RAM as well as 256K of pipeline burst cache, running Windows 95. My mouse is installed on COM1. I recently bought a Cardinal 28.8 Plug-n-Play modem. It installed correctly, but because of the PnP ability, Windows assigned it to COM3, IRQ 9. It works great in Windows, but because of the odd IRQ number, many of my DOS games don’t support it and I can’t play modem games with my friends. My COM2 serial port is available for use as it was where my old 14.4 modem was installed. Before I installed the 28.8, I removed the 14.4 from the device manager, etc., assuming that Windows would install the 28.8 there in its place. Unfortunately that wasn’t the case.

How can I force Windows 95 to put my 28.8 into either COM2 or COM4, IRQ 3? —J.W.

Answer: Plug-n-Play (sometimes abbreviated as “PnP”) devices are a bit of a paradox for the consumer. For most Windows users, they are a delight because they put the days of messing around with IRQs (interrupt request line, over which computer devices can send interrupt signals to the microprocessor) and COM ports behind us.

On the other hand, they are also inflexible and can become a headache for DOS game aficionados like you.

Under Windows 95, as you have discovered, they work great. Now the bad news: in your case the problem is unsolvable, unless you buy a new non-PnP modem.

To figure out the ins and outs of PnP and to get a definitive answer to your question, I asked one of my trusted experts, Kirk Reid, a senior technician at CompuSmart in Edmonton.

He explains how PnP works on PnP motherboards: “The BIOS (built-in software that contains configuration information about your system) scans available system resources (IRQs, COM ports, etc.) and asks PnP cards what resources they want. It then tries to find a fit. If all is OK, the configuration is stored in BIOS in a file called the ESCD. If the BIOS cannot come up with a fit, it shows that there is a PnP error.

“If you don’t have a PnP motherboard you can still use PnP devices.

“If you don’t have a PnP BIOS, then in DOS, you must run a software configuration program, like Intel’s ISA Configuration Utility. This does the same thing as PnP BIOS.

“When you run the install program, it detects all system devices and does a resource arbitration, like a PnP BIOS normally would. It stores the resource data in your root directory. When you boot up, the ICU setup driver is loaded in the config.sys file. This stays resident, and uses about 3K of conventional memory.

“If you have a PnP device that has a function you wish to disable (for example, the IDE controller on a sound card), with PnP BIOS you can’t do anything. There is no way to go into the BIOS and tell it to ignore the IDE controller,” says Reid.

If the BIOS doesn’t know best, as is the case here, you could install and run the ICU and steamroll the PnP assignments that your BIOS has already made. “This usually just confuses cards,” says Reid, adding, “PnP modems, especially Cardinal brands, will always ask for (the COM3 memory address) ‘3e8-3ef’ unless it is not available.”

So, avoid PnP modems if you’re an avid DOS gamer.

If you are strictly working in Windows 95 (where standard IRQ does not matter), you should not run into any problems.

A couple of final notes from Reid: “PnP sound cards seem to be OK, provided the IRQs the card asks for are available. There are problems here too, but stick to Creative Labs products. They seem to be the least problematic.”