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Installed additional parallel port-co...

Trish's Escape from Hardware Hell Help Board » Hardware » Printer, Scanner, Camera and USB » Installed additional parallel port-computer doesn't recognize the original parallel port - Help « Previous Next »

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James Sterling
Posted on Monday, October 23, 2000 - 8:27 am:   

I installed an additional parallel port, set the jumpers and it works properly. My problem is the original parllel port is now not recognized by the computer. My intent was to prevent switching cables to support a printer/scanner, and an external CD Writer. Is there any help for me?
Posted on Monday, October 23, 2000 - 10:41 am:   

yes. take out the p/p card and get an a/b switch for parallel ports. hook up the computer to the scanner, then from the scanner to the printer. when you want to use the cd writer, just flip the switch and presto! your there.
Posted on Monday, October 23, 2000 - 11:58 am:   

It's difficult to give specific advice without more info on your OS, PnP status, controller type and driver. Here're a few general ideas that may give you some hint's in solving the problem.
You may be having a system resource conflict. LPT ports use 3 kinds of resources. 1)DMA - direct memory access. 2)IRQ - interrupt request. 3)I/O address - memory location of driver.
Typically an LPT1 port has DMA 3, and IRQ 7 or 5. IRQ7 often starts at I/O address 0738 and IRQ5 often starts at 0278. First thing to do is check your system resources to make sure LPT1 and LPT2 each have a different IRQ and DMA setting.
Most modern systems have 8 DMA channels, and you probably find 6,7 or 8 available. If LPT1 has IRQ 7, assign LPT2 to IRQ5, or vice-versa. If you assign LPT2 to an IRQ other than 7 or 5 you're likely to create more problems. Don't worry about I/O address because this will be set auto-matically when you set the IRQ and DMA.
If you don't have a PnP OS and PnP port card, you may need to set jumpers according to the OEM documentation.
If you're running a DOS-based OS like WIN95/98/Me, you can check system resources something like this: Click Start > Programs > System Tools > System Information. Inside System Information look for the "components" listing on the left. Click on the + sigh to expand the components list, then click on "ports." Scroll the list until you find LPT1 and LPT2. Make sure each LPT has a different IRQ (7 or 5) and a different DMA, for example 3 and 6. Don't forget to check the name of you driver for reference. It'll porbably be lpt.vdx or something similar.
Probably not a good idea to start playing with IRQs and DMAs until you've backed up you registry and configuration files. You should do this anyway in case you have future unrelated problems. Hope this helped. Best Wishes, Tom
Posted on Monday, October 23, 2000 - 12:37 pm:   

James, since posting my message above on possible resource conflicts, I see I've made a serious typo error I need to correct. For LPTs, IRQ 7 typically has an I/O address range beginning at 0378 - NOT 0738 - as I mistakenly stated above.

Also, one more thought. Some older sound cards, like SoundBlaster Pro, often like to use IRQ 5 and/or IRQ 7. Might check to see if you have an IRQ conflict with a sound card.

You could also have a DMA conflict with a hard drive, DVD, CD-ROM or sound card.

Best Wishes, Tom

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