• Please review our updated Terms and Rules here

My first IRQ conflict! Need some help.


Veteran Member
Nov 28, 2022
Just installed a shiny new copy of Windows 95 onto a WinBook FX I just got in from eBay. Laptop needed a new hard drive and has a hinge problem I need to check but it’s otherwise working.
I’ve got an audio issue though. Seems like Windows knows what it is (it’s one of the Vibra 16 chipsets). Driver fails to load with a classic IRQ conflict with the parallel port.
So, I’ve never actually had to fix one of these before, so I’ve got no clue what to do. Can anyone help out?

Also one of the other "basic configurations" for LPT1 may include one that doesn't use an IRQ. Because parallel port polling mode should only poll when the port is being actively used (e.g., during a print job) it may not be as bad as it sounds.
I tried changing the Sound card’s IRQ to 5 and also keeping it at 7 and changing the parallel port to a different non-conflicting config but it didn’t fix the issue.
If it helps, the sound chip in this laptop is specifically a CT2505 Vibra 16. I couldn’t find any specific drivers for it from looking online unfortunately.

As well as that, the only drivers WinBook had up for this model were for an ESS card that this one doesn’t even have.
Can you run the software like diagnose or ctcu to configure it, like it's a stand alone vibra 16?
Windows 95 is supposed to have plug-and-play to automatically sort this kind of problem.

I bet the driver for the sound cad is not the correct one. I would check that. Also, try reseting the BIOS to defaults, just in case you changed some IRQ assignments there by mistake.
Ctcu and the DOS setup both say they can’t be run under the windows 95 dos mode.
Diagnose.exe runs but throws this error when I hit auto detect:

Here’s BIOS options. I set everything in windows to match. Also checked parallel and bios is using IRQ 7 so I set that as well. No conflicts.

BIOS options should all be default as the CMOS battery is dead (1.9v when should be 3v)

Also, selecting 260H in the diagnose app, it gives this error:
I would try explicitly loading BIOS defaults, and not just assuming they are being loaded because the CMOS battery is faulty.

Also, try disabling in BIOS the IrDA and the modem, and then let Windows 95 do it's plug-and-play magic.

If that fails, you probably may be loading the incorrect driver in Windows for that sound card.
Try loading UNISOUND in DOS mode and see what sound hardware you actually have. It might not be the one Windows thinks it is (unlikely but worth checking). You might want to hunt for better drivers anyway.

Try disabling "PnP OS" support in the BIOS. Often, the BIOS does a better job at configuring PnP devices than Windows 95 does. Otherwise, try using Windows 98, it may just work a lot better. Generally, I would recommend using Windows 95 for machines older than 1995, and Windows 95c for machines older than 1996, unless you want to spend time looking for updated drivers.

Also, note that Windows assigned the I/O base address 260h in your first screenshot. That address is unlikely to work with many DOS programs and will stay even if you boot into DOS mode.

You can also just disable the parallel port in the BIOS if you don't need it. That would free up IRQ 7, removing the conflict.
Here's the full specsheet direct from WinBook, it's a Creative CT2505: https://web.archive.org/web/20081003021629/http://www.winbookcorp.com/support/fx/fxspecs.htm
From my research, each different CT variant of the Vibra 16 (which is what the CT2505 is, although there were multiple variants of it) may need different drivers. I've found drivers for some of the other variants but not the CT2505. Windows 95's PnP driver is my main suspect right now, but I can't find an alternative anywhere to try.
Despite what WinBook says this has, the only 95 drivers they provide for sound are for the ESS 1688??? I tried the ESS 1688 PnP driver just in case and as expected it doesn't work, Windows detects it as a Creative card... not sure what was up with that.

I'll give UNISOUND in DOS a try later today though just to verify the card works though.

I loaded BIOS defaults and nothing changed.

If all else fails, I'll try Windows 98, but I do find 95 to be faster on a 1996 Pentium system than 98 would be. It's only got a 133MHz non-mmx Pentium 1 and 32MB of proprietary (ugh) RAM, so I can't upgrade it much.

I can't disable the parallel port, I use LapLink over parallel as my main method of file transfer. I can change its settings in BIOS though to use IRQ 5.
You could try loading UNISOUND in AUTOEXEC.BAT to initialize the card and then see if Windows 95 picks up the resources from there (or install its non-PnP drivers). Probably not a good solution, but it may work. Vogonsdrivers has lots of drivers for you to try though.

Since you already have the IE4 shell extension and IE5 installed, you got most of Windows 98-level stuff already; switching should not be much slower at this point, especially when configuring it correctly (TweakUI and friends). But I understand your reluctance, I stayed on Windows 95 on similar hardware for the same reason. Windows 98 makes it easy to install far too new software (such as DirectX 9.0).
I just found a driver here I'm going to try once I get home later today, seems promising: https://www.oldergeeks.com/downloads/file.php?id=84
vongonsdrivers returns no results when I search for CT2505 or just 2505. I did try a few drivers from there, but all the ones I could find were for Win3.1/DOS.

And on Windows 98 - it's not just speed, it's also that I already have many Windows 98 laptops that have better suited hardware for the OS, 95 just seems like the right pairing for this. And it also boots much quicker... 98 takes its sweet time on my ThinkPad 385XD with a Pentium MMX-233.
Driver I found was a bust. Seems like the driver it supplied WAS the PnP one as it showed as updated, but the driver itself didn't change. Still shows that error.
DOS sound is also not working. Parallel is though, used LapLink to get the files over.
Question then: if 260h is weird and nonstandard, what settings should I put in BIOS for the card?
Gonna try UNISOUND next right now.
The standard resources for Sound Blaster compatible cards are I/O base 220h, IRQ 7 or IRQ 5, DMA 1, HDMA 5 or HDMA 1 (some Vibra 16 cards with broken high dma). I believe DIAGNOSE will set up the card and write the configuration into the BLASTER environment variable.

However, UNISOUND will read the BLASTER variable and configure the card accordingly. Unisound must be run in plain DOS.

Try the following configuration, and if you have issues with 16-bit audio, replace "H5" with "H1" (my Vibra 16X is such a broken card):
Then test audio with some DOS programs, without booting into Windows.

Parallel LapLink transfers are a non-issue, the IRQ conflict does not matter as long as you are not trying to play audio while transferring data. The I/O addresses can never conflict and IRQs are only used while the respective device is in use.
Still not working with that config or UNISOUND. Really not sure what's up at this point...
I'm going to make a video going over in detail everything I have configured, I'll link it here and then hopefully I just have something set wrong.
You need to set the sound's base address to 220h, IRQ 5, DMA low to 1, and DMA high to 5 in the BIOS. The Vibra chip in that machine may be pre-PnP and requires initialization in DOS using Creative's DIAGNOSE or UNISOUND with the /NOPNP switch.