Avoid the first PCI slot?

[tbooth]

Normally I don't use the first PCI slot to avoid conflicts with my video card but I'm in a situation where I need to place a SCSI controller in the first slot of my Abit NF7-S (either that or rearrange my entire watercooling setup). Should I expect any issues or degraded performance by doing so? Anyone else using the first PCI slot and AGP slot without issues?

 

[Jeff7]

In the olden days I would get conflicts, but they were rare, even when I had several devices sharing IRQ 11 under Win98SE. I can't say I ever saw performance decreases though - the conflicts I did experience would always just make one device (or both) stop working entirely.
In my experience recently, WinXP, along with modern motherboards, are much better at sharing IRQ's. And, you also get a lot more IRQ's with new motherboards - don't remember if it's ACPI or APIC (don't remember what either of those means, of if they're even relevant), but whatever it is, new motherboards give you more than 15 IRQ's, so your devices get a lot more settings to play with.

For the record, my system currently has 2 devices each on the following:
IRQ 16: TV Tuner, VIA Rev5 or later USB Universal Host Controller
IRQ 19: Radeon 9800 Pro, VIA Rev5 or later USB Universal Host Controller
IRQ 20: nVidia APU, OpenHCD USB Host Controller
IRQ 21: nVidia codec interface, IEEE 1394 controller, Enhanced PCI to USB Host Controller
IRQ 22: nVidia NIC, OpenHCD USB Host Controller

 

[JerryT87]

Lol, I thought the same thing when I saw that my video and Audigy ZS were on the same IRQ after my install, but no problems so far. (cross fingers)

 

[Bozo Galora]

APIC gives 24 (0-23) hard interrupts when correct HAL is selected at install
WinXP then can assign 256 (0-255) VIRTUAL IRQ's in a dynamic manner after POST.
Thats why you may find 5 or 6 items on IRQ 9 or 11
ACPI gives advanced power on/off/standby/wake options


(Quote)
--The PC 2001 Specification calls for all compliant mainboards to
support "APIC", which FORMERLY was used with Multiprocessor Hardware,
but now is also used with single processor mainboards as well. APIC
(NOT ACPI) stands for Advanced Programmable Interrupt Controller.

Multi-Processor Operating Systems (Such as XP, and Windows 2000) can
take advantage of APIC to increase the available interrupts (up to IRQ
23), regardless of whether the hardware has one or more CPU's.

Because of the large migration to a multi-processor operating system
such as XP, multi-processor features may be unfamiliar to single
processor users.

Because your mainboard is PC 2001 compliant, XP should have installed
the ACPI Uniprocessor PC Hal.

To sum it up, both ACPI (which MSI sometimes misnames IPCA in the
Bios) and APIC should be enabled in the Bios. Then, XP should install
the "ACPI Uniprocessor PC" Hal.

Some older PCI cards MAY not support the manner in which XP allocates
IRQ's under APIC. In that case, it may be necessary to disable "APIC"
in the Bios and re-install XP, but this should only be done if one is
certain that APIC is the problem. Regardless, ACPI (MSI's IPCA) should
be left enabled. If APIC is disabled and ACPI enabled, XP will
(should) install the Advanced Configuration and Power Interface (ACPI)
PC HAL.---

 

[tbooth]

Awesome, thanks for the info guys. Guess I can get rid of my legacy superstitions .

 

[JimPhelpsMI]

Hi, The original IBM PC and most of it's clones had one slot that was wired differently to plug a communications device card into. The present aversion to using one of the slots may be a misconception. Most mother boards I have used, and they are many, have all of each type of slots (PCI, AGP, etc.) wired in parallel, so it would not matter which ones you use. If your MB manual does not mention such a thing, you can probably assume that there is no problem. Jim

 

[3chordcharlie]

The only real reason to leave slot one open is to allow space for your video card fan, if applicable. It's not a big deal.