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IRQs, PCI cards, and Windows 95

Posted on 1998-04-25
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Last Modified: 2013-11-09
I have the following cards in my Pentium 233MMX Tyan motherboard with Windows 95:

Intel Etherexpress PCI network card  (IRQ9)
Adaptec 2940UW SCSI PCI controller (IRQ11)
Creative Labs Sound Blaster AWE32 (IRQ5)
Matrox Millenium PCI video card (IRQ9)
Microtek E6 scanner SCSI card AIC-6x60 (Adaptec) (IRQ12)

And of course, COM1 (IRQ4), COM2 (IRQ3), LPT1 (IRQ7)

along with 2 Maxtor EIDE hard disks.

My questions are:

1) Am I correct in that PCI cards can share the same IRQ without any problem?  In the above you will see the network card and the video card sharing the same IRQ 9.

2) If I check "Control Panel > System > Properties > Device Manager" and check the IRQ assignments, I also notice that there are 2 devices using IRQ14:

Standard Dual PCI IDE Controller
and
Primary IDE controller (single fifo)

Should this be a concern or worry?  I.e., two on one IRQ?

3) I notice that two devices in the "View Resources/IRQ" list have tiny little blue "i" 's in a white circle, next to the device icon.  What do they represent?  Since I have two SCSI controllers on this PC, I see the SCSI icon twice in this list (for IRQ 11 and 12), however only one has the little "i" next to the SCSI icon.  Why the difference in icons between the two SCSI devices?

Thanks.
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Question by:Kapusta
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khemicals earned 70 total points
ID: 1134598
1. NO DEVICES SHOULD EVER SHARE IRQ's... yes there are some that can.... but in general and as a rule don't do it... it is better in the long run and helps avoid any future problems. so don't share irq's.... you are limited to the 16 you have

2. that is normal... nothing to worry about... for your purposes consider them as the same device

3. the i means that there is a conflict (whether or not the device manager says there is one or not) and the little i can be the difference between a working device and a non-working device. from the info given above i can't see why there is an i next to the one... maybe something is using an irq and not reporting it properly (sound cards are notorious for this).

4. why 2 scsi cards? the 2940UW is capable of 15 devices if i am not mistaken and has plenty of power for all of your possible scsi devices.... the 2940UW is capable of driving the scanner so long as you have the scsi card's aspi drivers installed... i check the microtek web site to verify this... all you need to do is run scsi cable from the card to the scanner and remove the termination from the external device and from the scsi card to the external device... this in general should work... i don't know if you even need to deal with termination as to the external ports on the 2940 or not so check your documentation... this will not only free an irq for you... it will also free up an expansion slot... both very valuable.

i hope all of this helps

-khemicals
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by:Kapusta
ID: 1134599
 >> all you need to do is run scsi cable from the card to the  scanner and remove the
  >> termination from the external device and from the scsi card to the external device...
  >> this in  general should work...


I believe you overlook the fact that the 2940UW uses a high density external connection, whereas the Microtek scanner uses the older low density pin connection.  When I talked to Microtek, they stated that the 2940UW is too fast for the scanner, and recommended I stay with the second proprietary SCSI card.

 >>1. NO DEVICES SHOULD EVER SHARE IRQ's... yes there are some that can....
 >> but in general and as a rule  don't do it...

So what do you do when you have no more IRQs?   Which is the case with my system.


 >> 3. the i means that there is a conflict (whether or not the device manager says there
 >>  is one or not) and the little i  can be the difference between a working device and a
 >>  non-working device. from the info given above i can't see  why there is an i next to
 >>the one..


Actually I have 3 devices that have little "i"s in the icon...

IRQ5 - Creative Labs Plug N Play Blaster 16
IRQ10 - Standard IDE/ESDI Hard disk controller
IRQ12 - Adaptec AIC - 6x60 ISA Single Chip SCSI controller

and my Matrox video card and Intel Ethernet PCI cards share IRQ9, with no "i"s or conflicts.

The hard disk controller concerns me the most.


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by:khemicals
ID: 1134600
i didn't overlook that... all you need is a special cable... look at this page on the adaptec site: http://www.adaptec.com/support/configuration/connect.html
that should solve the 2 scsi card problem and free one irq

when you have no more irq's there is nothing that you can do... that is a limitation of the current pc design made for backwards compatability.... if you don't wanna deal with irq's get a macintosh.... sorry but there isn't a simple solution..... however you could use a scsi hard drive and cd-rom (put any and all devices that are connected to ide into another system and go completely scsi) and then use scsi cd-rom and hdd.... then you can free irq 14 and if you are using the secondary you could also free irq 15 that way... .would have to disable them in the bios and then tell it to change the boot order to a,c,scsi ( assuming that you don't need a bios upgrade first to do that.)

this is your current irq situation:

0. timer
1. keyboard
2. cascade
3. com2
4. com1
5. sound card
6. floppy
7. lpt1
8. clock
9. ethernet card/video card
10. ps/2 mouse
11. AHA 2940 UW
12. microtek
13. coprocessor
14. primary IDE
15. secondary IDE

this is what it would be if you switched to scsi hdd and cd-rom and moved the scanner to the adaptec:

0. timer
1. keyboard
2. cascade
3. com2
4. com1
5. sound card
6. floppy
7. lpt1
8. clock
9. ethernet card/video card
10. ps/2 mouse
11. AHA 2940 UW
12. free
13. coprocessor
14. free
15. free

so don't overlook that as a possible solution... it would give you three more irq's without breaking any rules.


i would not worry about the i's unless something is working improperly.... some times things won't be 100% optimal but will still work. there is no need ot be worried about the hd controller unless you are having hard drive problems... which you shouldn't be as irq 10 is not used for ide hard drives... so the irq is being assigned to the sound card maybe? (if it has a ide port on it) and that is the same reason that could be causing the conflict on the others as well..... a good way to test this is remove the sound card from the OS in device manager, turn off the system and remove the card, reboot and see what happens.... sound cards are no fun to work with at all and are usually the culprit in a situation such as this

lmk what you think and do about this

-khemicals


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by:Kapusta
ID: 1134601
Thanks for the continued information.

Do I assume correctly that even if I were to switch from a COM mouse to a PS/2 mouse and then disable COM1 from my BIOS, I would NOT be freeing up an IRQ?


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by:khemicals
ID: 1134602
yes... i just assumed that you had a ps/2 mouse... so consider irq 10 free if it weren't being used by the controller with the little i... tell me what happens if you remove the sound card... i have a feeling that it is causing the conflicts
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by:Kapusta
ID: 1134603
>> i just assumed that you had a ps/2 mouse... so consider irq 10 free if it weren't
>> being used by the controller with the little i.

Actually what I was asking was, can I buy a PS/2 mouse and trash my COM mouse, and then disable COM1 and gain an IRQ?  Or would I simply be taking one step forward and one step back?

I also don't understand why there are four IRQs for the hard drive controller(s):

IRQ10 Standard IDE/ESDI hard disk controller
IRQ14 Standard dual PCI IDE controller
IRQ14 Primary IDE controller (single fifo)
IRQ15 Standard IDE/ESDI hard disk controller

Why in the world do I need 4 (3?) IRQs for the hard disk controller?

I have 2 IDE hard drives on my primary cable, and 1 IDE CDRom on the secondary cable.
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by:khemicals
ID: 1134604
this is what is up with your IDE controllers:
Primary IDE is IRQ 14 (your hard drives)
Secondary IDE is IRQ 15 (your CD-ROM)

these are the normal IRQs for these resources and are not normally reassigned and/or changed

don't worry about the 2 controllers on IRQ 14... you have 2 drives on that IRQ and each has its own controller (IDE stands for Integrated Digital Electronics) or rather the controller is on the drive itself. so each device on the primary IDE shows up as using the same IRQ as it should be... and since you have only one CD-ROM drive it is the only controller showing up on IRQ 15... the secondary IDE port

This is what i think about IRQ 10 and its disk controller... not positive as there is only one way to tell... but you haven't done what i suggested above so I have no way of knowing...

the device on IRQ 10 is most probably your sound card. most older and some newer sound cards come with an ide controller on them for a cd-rom drive. there is probably a jumper on the sound card to disable it.. and if not you can do it manually inside of windows by choosing disable the device in this profile under device manager... so you should only be using 2 IRQs for a total of 3 IDE devices and 2 controllers.

on the mouse issue... not really a good idea to disable com and parallel ports to gain irqs... u may need the port someday... you would be shocked... anyways I would stick with the serial mouse on com 1... and just make sure that ps/2 mouse is disabled in the bios... that should allow you to use irq 10... and if you want to add a modem to your system buy an external modem and install it to com 2... that way you are using a pre defined irq... its a good idea for any user that may be haveing problems with the irq limit

i think that answers all of the above... ask more if you need

-khemx
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by:Kapusta
ID: 1134605

 >>This is what i think about IRQ 10 and its disk controller... not positive as there
 >>  is only one way to  tell... but you haven't done what i suggested above so I
 >>  have no way of knowing...


I apologize for my tardiness,... I did pull the sound card from my PC, then rebooted Windows 95.  When Win95 came back up, it reported that it found a new device...oddly, it auto-detected a floppy drive controller!  Win 95 then wanted to reboot again after the new device was installed.  When Win95 came back up, I checked Device Manager.  IRQ5 (where the sound card was) now showed nothing next the the number 5.  The two shared PCI devices on 9 became separated...one stayed on 9, and the other moved to IRQ10.

Here's the IRQ assignments AFTER removing the sound card:

3 COM2
4 COM1
5
6 Std. floppy disk controller
7 LPT1
8 System CMOS/real time clock
9 Intel PCI ethernet
10 Matrox Millenium PCI video card
11 Adaptec AHA2940 SCSI
12i Adaptec AIC-6x60 ISA single chip SCSI card
13 Numeric data processor
14 Std. dual PCI IDE controller
14 Primary IDE controller (single fifo)
15 Std. IDE/ESDI hard disk controller

The only little "i" that remained was on IRQ12...the Microtek ISA SCSI card.

Also, I discovered that this exercise rendered my modem (on COM2) disabled.  When I tried to dial out and connect to the Net, I was informed that Win95 could not detect a modem.

I then shut my PC down, reinstalled the sound card, rebooted, and now everything is back to where I was before I pulled the sound card.  Modem is working again.

I'm not sure what this tells you?

I ordered the Adaptec high density to low density connector today from CDW.  I will see if this adapter will work.  If so, I will pull the Microtek SCSI card out, freeing up an IRQ.
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by:khemicals
ID: 1134606
what it tells me is where that extra drive controller was coming from so we can disable it...  disable the hdd controller that is on irq 10 ... this should free 10.... unless the above happens again.... with the sound card back in it takes up 5... or at least it should... that is the default. the modem you may have to reinstall if you do that... but it was only a test to see what would happen. i would (if i were you and needed more irq's) purchase a scsi cd-rom... they cost about 100... and that will free up irq 15 when you disable the secondary...
other than that your only next thing would be to go all scsi and free irq 14 too

-khemx
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Author Comment

by:Kapusta
ID: 1134607

>>  i would (if i were you and needed more irq's) purchase a scsi cd-rom...

I was thinking about this myself recently, however, my concern is whether the SCSI CD Rom drive can be accessed outside of Windows 95?  IOW, if I were to boot to a command prompt only, are there drivers that allow me to access the SCSI CD from DOS (no Windows loaded)?

>>disable the hdd controller that is on irq 10 ... this should free 10

I will try and see what happens.
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by:khemicals
ID: 1134608
yes there are... you would not want those to load when you start windows for compatability reasons... but you could always make 2 autoexec.bats and 2 config.sys and make bat files to copy them before you reboot
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by:Kapusta
ID: 1134609
Here's what happened when I removed the device on IRQ10...

I removed the device on IRQ10 from Device Manager, then I rebooted Win 95.  Upon reentry, Windows 95 stated that it found a new device (hard disk controller) and wanted to install it.   I answered "No".

When Win 95's desktop appeared, I then checked out the Device Manager, and 10 was missing from the IRQ list.  Oddly, IRQ 9 still was being shared by two PCI devices.

Upon exploring the Device Manager, I noticed that under "hard disk controllers", I now have a yellow exclamation icon where the previously removed driver was, and what is most odd is that this device is listed as "Creative 32 PNP".  That's my sound card being listed under the hard disk controllers!
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by:khemicals
ID: 1134610
like i said... the controller is your sound card... most sound card have ide ports on them for support of old cd-rom drives that most people with newer systems don't use anymore... my solution for you would not be to remove the device (as it is there and windows PNP will always find it and install it from now on) but instead to disable the device in your current profile... just doubleclick on the device under device manager and disable it in your current profile... but only do so to the part under the hard drive controllers and lmk what happens
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by:Kapusta
ID: 1134611
>> my solution for you would not be to remove the device (as it is there and windows
>> PNP will always find it and install it from now on) but instead to disable the device
>> in your current profile... just doubleclick on the device under device manager and
>> disable it in your current profile...

I have done as you have suggested, and when I reboot, and then check Device Manager, I find under "Hard disk controllers" a red X through the "Creative SB32 PnP" item.

However, if I double click on "Computer" and take a look at the IRQs, it still shows IRQ10 as being used by the "Creative SB32 PnP".

In other words, the IRQ (10) is still being claimed by the "disabled" device.

After playing around with the "Properties" page for this device, on the "Resources" page, I must have done something right, for after clicking something, Win 95 said "you must reboot your PC...".  When I did, and came back up, the "Resources" page for this device became disabled, and also resulted in the IRQ 10 disappearing from the IRQ list.

Hurrah!  I freed up one IRQ!

Thanks!

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by:khemicals
ID: 1134612
the resource was still being used as the driver files were still being loaded... the x is just to show you that it is disabled
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by:Kapusta
ID: 1134613
Once last comment...

I ordered the Adaptec 68 to 50 pin external adapter, as you suggested via your reference to visit: http://www.adaptec.com/support/configuration/connect.html

The adapter arrived today, however I believe you overlooked something...

This adapter simply converts from 68 pin high density to 50 pin HIGH DENSITY.   The cable to the Microtek scanner, however, is a regular DB25 style 25 pin cable (where it plugs into the PC), and a Centronics 50 pin female (where it plugs into the scanner).  In other words, this adapter is of no value.   I will have to return the adapter.
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by:khemicals
ID: 1134614
call up adaptec.... there probably is an adapter that does what you want... if they don't have it i would almost bet money that www.blackbox.com will have it. they have everything. I am sorry i pointed you in the wrong direction... i am kinda new playing with scsi myself... anyways... i am pretty sure black box will have what you need as they make devices that break every rule there ever was in computers.... i have looked and i think i know what you need but probably best if you call them and see if they can help you find exactly what you need
-david
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by:Kapusta
ID: 1134615
>> call up adaptec.... there probably is an adapter that does what you want...

I still remember a technician at Microtek tell me that the AHA2940UW is too FAST for a flatbed scanner, even if I do find the correct adapter.

Nevertheless, thanks for your assistance.  You have been very helpful.
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by:khemicals
ID: 1134616
I just can't see how that would be a problem... there has to be a way to do it.. and it wouldn't surprise me if either blackbox or adaptec could help you... the worst thing that would happen is that they would say you can't do it... and then at least you can think hey... i tried to free that one more irq that i can use... there is no need for the extra card in my mind... there has to be a way
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