Printer and Soundcard - Same Irq

I have a soundblaster 16 non-pnp card and my lpt2 default printer both working fine with no conflicts in win95, but they both have the same irq 5. They both obviously have different IO addresses, but how can they both be working simultaneously? Soundcard has 2 dma settings...1 and 5 and 2 separate IO addresses too. The lpt2 port shows no irq or dma settings....
firemannAsked:
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larezCommented:
It is possible to have shared irq's under certain circumstances, and with certain devices. However it is not possible to USE both deviced that have shared irq's, at the same time.  Have you ever tried printing to LPT2 while you were playing sounds; this should not work (careful, this may cause your computer to lock up). Shared irq's are possible when one or both of the devices are seldom used. Generally speaking, though, you should try to give each device it's own seperate irq, this reduces potential problems. But hey, if it ain't broke, don't fix it.
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firemannAuthor Commented:
My understanding of IRQ's, led me to believe that what you did (use both devices at the same time) is not theoretically possible. But I guess theory is not always true in practice :) As for if they depend more on DMA, I really don't know, but the logic behind that statement seems sound. When a device uses it DMA channel, it literally communicates with the memory, directly, by transfering information to and from memory directly, bypassing the CPU. IRQ channels, on the other hand, "request", ask the processor for attention/use; the processor can get confused when more than one device has the same IRQ and they both "request" attention/use at the same time.
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larezCommented:
Thanks for your help Larez, but you didn't tell me anything I didn't already know...still want to know reasons why it was working even if they were not technically working at the same time...ie. sharing dma time.. Could it be that the pci bus takes care of some address conflicts if the devices don't interfere too much
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firemannAuthor Commented:
Sorry I couldn't be of more help. I'm not sure about your PCI bus hypothesis... If I think of anything, I'll be sure to tell you.  BTW, I get most of my information from:
http://www.sandybay.com/pc-web/
Maybe there is some information that may be useful to you, there. Good luck: )
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larezCommented:
firemann...

Please, before we go any further with this problem I would like you to give me the list of your Free IRQ in Device Manager.

1) Right click on My Computer
2) Select properties
3) Select Device Manager Tab
4) Once In just click on Properties from the bottom left

Take note of all FREE IRQ's.

If you cann tell me what are all the devices you have too, it will be helpful (Sound card Brand, Modem brand, etc...)

Will wait for your post, we will make it happening after.
Regards
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magigrafCommented:
Hmm, AFAIK LPT2 always use IRQ7. To configure it for IRQ5 you must
to do it manually in BIOS setup. Are you sure that LPT2 use IRQ5 ?
How did you know that ?
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busukaCommented:
You mstill have MSD with 95. See that it reports the same as your device manager. If It's not in your windows\command directory, then pull it off of your 95 CD.
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smeebudCommented:
Let me clarify further...I put a second parallel port card in and configured it to lpt2 and irq 5 and dma 1 .. I am using my printer on this port. My lpt1 is irq 7 and dma 3 and I am using  an external tape drive on this port. Originally my soundblaster 16 card was configured at irq 5 and dmas 1 & 5 and there were no apparent conflicts when working with any of the devices and they appeared to work concurrently... msd (when opened in dos mode)shows both irqs active at the appropriate no.s that I mentioned above.. rechecked all card for correct jumper settings...My bios doesn't have a configuration option for lpt2 only lpt1 and it is set to irq 7
I have a soundblaster 16 non pnp at irq 5 dma 1,5
         usr 56.6 internal modem at irq 3
         serial mouse at irq 4  
         parallel port card at irq 5 lpt2 dma 1
         on board parallel port at irq 7 lpt 1 dma 3
         free ports 10,11,12

One footnote..my win95 doesn't show the irq 5 to be used by anything..  parallel port card not showing up anywhere (there was no driver installation with the card ..just jumpers which would make sense)
I moved the soundcard to irq 10 and it shows up in the win95 resource area , but when it was set a irq 5 it would not showup...could the fact that there is no bios entry for lpt2 be the reason win95 is not picking up the irq 5
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firemannAuthor Commented:
Remove your printer card and your sound card.
Then remove there driveres in device manager.
Run hardware detection after removal to remove their entries from the registry.
Then, one at a time put them back in and either let hardware
wizard pick them up or reinstall them yourself.

Search you registry beforehand to make sure all references to them are gone.
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smeebudCommented:
Thanks for everyones help... I was looking for the reason why the 2 devices seemed to be working without any conflicts..I got some good comments but nobody is answering the question...everything was and is working and as a procaution , I moved the soundcard to irq 10...
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firemannAuthor Commented:
I guess no one knew the answer. We're used to fixing things here. If youfind out let me know.
Thanks:)
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