I try leaving empty slots below video cards for better cooling, but for everything else I don't really care.

Not a bad idea. Sometimes you are forced to put a card in a particular slot. For some reason, PCI network cards work best for me in the very last PCI slot 😀

Is doesnt matter that much.. And this: Sometimes you are forced to put a card in a particular slot. (because of IRQ problems) or needed a bus master slot.

Only where it matters, I perfer to give a (3D) video card as much room as possible even if that means the other cards gets squeezed together. I also dont use any slot brackets at the slots under the video card so it can suck cool air from the outside.

I usually put the soundcard on the last isa or pci slot, in order to reduce interference from rest of components inside the case,I remember reading an article back in a magazine back in the 90.

Allways done that since my 486 days.
Unless it's a desktop case, or I need to put too much hardware in a system.
Sometimes hardware does not permit you to do it. (SLI as an example)

I did a quick search about SLI before I installed the Voodoos and it seems it can work, however i did not tested because I don't have the SLI cable.

This is what it reads at http://www.3dfxzone.it/dir/3dfx/voodoo2/faq/#Q32 :

"Yes, Voodoo2 will function in SLI mode in non-contiguous PCI slots as long as the SLI cable is long enough to reach between the two cards. The current cable length is 3.1"."

Nahkri wrote:

I usually put the soundcard on the last isa or pci slot, in order to reduce interference from rest of components inside the case,I remember reading an article back in a magazine back in the 90.

Yes, I do this too because I read that it must be as far from the cpu as possible, or it would pickup noise.

You know that if you install only one module of ram it should be the one nearest to the cpu, or the slot with the lowest number, and that is supposed to better your performance, does something similar happens to videocards perhaps?

I put my PCI cards all at the bottom with the largest the lowest and the smallest PCI card nearest the video card

Is it true that the AGP slot and the PCI slot next to it share an IRQ? I read that somewhere on Vogons. Either way, I put a V3 PCI next to whatever AGP card is installed.

Multiple PCI cards can share an IRQ. I'm guessing the same goes for PCI/AGP. If you use IRQ steering you shouldn't have any conflicts on the PCI bus.

EDIT: https://support.microsoft.com/en-us/kb/182604

manbearpig wrote:

Multiple PCI cards can share an IRQ. I'm guessing the same goes for PCI/AGP. If you use IRQ steering you shouldn't have any conflicts on the PCI bus.

EDIT: https://support.microsoft.com/en-us/kb/182604

...but my SB Live! and my BT878 TV card keep hanging if they shared the same IRQ. I don't know if it had driver or hardware problems, I gave the damn thing to a friend and I don't have a reason to re-check it.

Funny, the BT878 has been quoted two times in this thread...

This is not a coincidence. My concern about this subject started when I installed a TV card and the PC took triple the normal time to boot.

There's several considerations in the expansion slot roulette and they usually preclude any thought to symmetry or air flow. There's the IRQ sharing; you get a handful of interrupts, maybe only 4 between your PCI slots and integrated PCI devices like ATA/RAID, USB, sound, and LAN controllers; and then there's the occasional issue with "slave" PCI slots lacking bus masters, more PCI slots than fully supported by the chipset. Slots can be physically obstructed by BIOS chips, jumpers and stuff, too, so some cards can't fully be inserted in some slots - mostly encounter this kind of trouble with ISA/VLB slots.

It can take a lot of tries to find the right devices to share interrupts. Even if something works at first glance, its functionality can be hindered, such as sound cards producing pops and glitches, or network cards losing connections when a USB device is operated, etc.

On my retro rigs I tend to put storage & communication controllers on the top and video & sound on the bottom, the latter as separate as possible to minimize EM noise and maximize airflow. I like the 'every-other-slot' approach when conditions allow, just because it gives me more room to manipulate the cards and to stuff excess ribbon cable between them. 😜

It is a good practice to leave room between cards for air flow and it makes servicing the machine easier plus it looks better 😉
In the end though we always run out of slots :s

133MHz wrote:

On my retro rigs I tend to put storage & communication controllers on the top and video & sound on the bottom, the latter as separate as possible to minimize EM noise and maximize airflow. I like the 'every-other-slot' approach when conditions allow, just because it gives me more room to manipulate the cards and to stuff excess ribbon cable between them. 😜

^this...totally agree. Of course it's not always possible but it is the model to follow for me in most cases.

Space around the video card, definitely, and I try to interleave short / shallow cards with others.

Also, since there are usually fixed mappings of the IRQs, I try to balance the usage, and avoid putting two very busy things on the same IRQ.

The "old style" IRQ assignment allocated up to 4 unused ISA IRQs - on an ISA + PCI system, you may have less than 4 available (disable an unused COM or LPT port to free).

The IRQs map to PCI INTA-INTD, and the assignments of INTA-INTD are normally rotated from slot to slot (as most devices simply select their own INTA line).

Onboard PCI devices also use these, so one or more slots will share with the USB, one will normally share with AGP, and if there is onboard PCI sound, one or more will share with that.

While PCI is supposed to allow seamless IRQ sharing, it doesn't always work that way!

Sound cards always at the bottom to reduce interference and bus noise, video cards get one or two empty slots below them for better airflow, everything else gets crammed together. If possible.