Homegrown computer


Dec 31, 2007
Intend to build my first homegrown computer, but getting a bit scared!

After reading in this very forum about the troubles one can get into when Sound- and Videocards begin to interfere with each other I am beginning to think it might not be such a good idea building it myself afterall.
Can anyone please give me an explanation about some of the IRQ's which I don't understand in the following table (copied from my existing computer).
No problem for the obvious device IRQ's, only 02, 03, 05, 05bis, 10bis, 11bis, 12bis, 14, 14bis, 15 and 15bis are all but clear to me.

- Do I really need all this, and are the doubles only a slovenliness of the Windows householding?

- How come 03 is not taken?

00 - System timer
01 - Keyboard
02 - Programmable interrupt controller
03 - ??????
04 - Com 1
05 - Intel 82371AB/EB universal host controller for PCI to USB
05 - IRQ holder for PCI steering
06 - Standard diskette station controller
07 - ECP printer port controller
08 - System CMOS/Real-time clock
09 - Soundblaster 16 or AWE 32 or compatible
10 - Conexant PCI modem emulator
10 - IRQ holder for PCI steering
11 - Diamond Viper 550
11 - IRQ holder for PCI steering
12 - Adaptec AHA-294X/AIC-78XX PCI SCSI controller
12 - IRQ holder for PCI steering
13 - numeric processor
14 - Intel 82371AB/EB PCI Busmaster IDE-controller
14 - Primary IDE controller (double fifo)
15 - Intel 82371AB/EB PCI Busmaster IDE-controller
15 - Secondary IDE controller (double fifo)

Configuration of existing system:

ASUS P2L97 mobo
Diamond VIPER550
64 Mb ram
SCSI controller
Scanner Agfa SCSI
HD Seagate IDE 10Gb
Modem Conexant (Rockwell) 56K intern
Floppy drive
CDRom Mtpr 40X

System to build:

Midi tower in Aluminium 400Watt power supply and 3 ventilators
Mobo ASUS A7M266
AMD Thunderbird Athlon 1.2 GHz with compatible heatsink and fan.
256Mb PC2100 DDR SDRAM
ASUS V7700Ultra Graphics card
Sound blaster PCI (not sure yet about the exact type, I don't need surround stereo)
CD-RW Plextor "Plexwritor" 12X10X32
Two HD drives 30 GB 5400 rpm (noise) ATA 66
Jaz drive 2GB (recup. Old pc + existent SCSI card)
PCI Controller card for external cable modem (normal use of the internet and games)
Modem Conexant (Rockwell) 56K intern (only for FAX. Usage)

Now I think one can understand why I am scared of possible IRQ conflicts.
Would be greatfull if anyone could help here guys.
Thanks in advance.


Dec 31, 2007
Just a quick note on why you are seeing the doubles as this could be a long discussion.

You are seeing Bus Mastering with programmable interrupts showing up. Meaning you can have multiple devices requesting the same interrupts and the bus master is controlling which gets access and when.

IRQ 3 is not used, because nothing has asked for it or nothing already installed may have the addressing to get pushed there.

Go ahead and build your new system. Stick to PCI as much as possible and you shouldn't have a problem.