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need help w/ 64 bit PCI slots

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all420

Registered
Joined
Nov 21, 2001
Location
San Jose, CA
I recently purchased a P4DC6+ from SuperMicro.


P4DC6+.jpg


The two PCI slots farthest to the right are 64 bit. I thought that they were backwards compatible with 32 bit pci cards. However, I tried to put one of my 32 bit cards in there and it wouldn't fit. Are the 64 bit slots supposed to be backwards compatible? If they aren't, is there any way I can use a 32 bit card in the 64 bit slot? maybe an adapter of some kind? I really need those two slots. Any help is greatly appreciated. Thanks in advance.
 
No, you are pretty much out of luck. I've never seen a slot that was 64 and 32bit compatible, nor have I seen any adaptors. We have a couple boards w/ 64 bit slots at work.

Take a look around Pricewatch or something, you may be able to find the device you need in 64bit PCI flavor. :)
 
These are 64-bit 66MHz slots which uses 3.3V signaling. They are not backward compatible with most 32-bit 33MHz 5V PCI cards. However they will work with the newer 32-bit universal PCI cards (support both 3.3V and 5V signaling) like Soundblaster Audigy or Intel Pro 100 + LAN card etc...

As for newer cards, more and more of them will be either universial or 3.3V cards, as the PCI Spec 2.3 requires all new cards be either universial or 3.3V only.
 
Sure you can use 32bit cards in those slots. What you have to understand is that they are 3.3v only slots. That means that in order for a card to work in those slots it must either be a universal card (meaning that it is keyed for either 3.3v or 5v operation) as skyfox mentioned or a 3.3v only card. The thing that stops you from inserting your 5v PCI cards into those slots is the keyway in the slot. This is a safety feature meant to prevent the insertion of 5v only cards into the slots which could cause damage. cards that support 3.3v operation have a notch cut out for that keyway and will go into the slot and should work just fine.

Right now, I'm using a Fasttrak 100 TX2 in one of those slots on my P4DC6. The Fasttrak 100 TX2 is a universal (meaning it has notches cut for both 3.3v and 5v keyways in it) 32bit 66Mhz card. However, 33Mhz cards should work as well. With a 33Mhz card the particular PCI bus that slot is on will default back to 33Mhz operation. Here's a nice page that you might want to look at regarding this. It's shows diagrams of cards and slots and where the keyways are located. Have a look at it.

http://sunsolve.sun.com/handbook_pub/General/PCI_Info.html

Here's another page with fewer diagrams but a more detailed description.

http://www.techfest.com/hardware/bus/pci.htm#1.0

For future questions you might want to visit the forums over at www.2cpu.com. There are a few of us over there running dual P4 Xeon systems and most of us are using one of this Supermicro family of motherboards (P4DC6, P4DC6+, P4DCE, or P4DCE+). Pop over there sometimes and join team Xeon as we like to call oursleves. :)

Good luck with your board and congratulations on choosing what some of us consider to be one of the finest motherboard currently available.
 
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huh! I took a look at the server board we have at work, and it is supposed to have 64 bit PCI- well I look at the slot and it sure looks like a regualr PCI card won't even fit in there. Did I miss something or is this just a bad board? It's pretty old I think.
 
Monster of Rock said:
huh! I took a look at the server board we have at work, and it is supposed to have 64 bit PCI- well I look at the slot and it sure looks like a regualr PCI card won't even fit in there. Did I miss something or is this just a bad board? It's pretty old I think.

Well, what kind of 64bit PCI slots does it have? 5V or 3.3v? If it's an older board it most likely has 33Mhz 5V 64bit slots. It's mostly the newer boards Like the I860 P4 Xeon boards that have 66Mhz 3.3v slots. Technically in order to comply with the latest PCI specs in ordr to support 66Mhz operation the slots must use 3.3v signaling. Hence the reason you see these slots on the I860 boards keyed for 3.3v. The older 64bit slots are usually keyed for 5v operation and only support 33Mhz operation. Really though you don't have to worry about whether it's 66Mhz or 33Mhz because the slot and the card will negotiate this between themselves and determine whether 66Mhz operation is supported or not by the state of a certain pin on the card. So, 33Mhz cards should work in a 66Mhz slot provided they support 3.3v and thus fit the keyways in the slot. As for the use of a 32bit card in a 64bit slot, provided the the keyways and signaling voltages are compatable as already described, you simply plug the card into the part of the slot that it fits in and the additional part of the slot that is used with 64bit cards remains empty. The motherboard will determine whether the card uses the 64bit extension or not and will operate in 64bit mode if the card is a 64bit card and supports it and if not will default to 32bit mode. Anyway, go back and look at that page at SUN that I linked to earlier. It has some drawings of slots and cards and tells you which cards can be used in which slots.
 
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