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  1. #1
    Übercaffinated Member Caffinehog's Avatar
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    64-bit PCI slots....

    Can I use standard 32 bit PCI cards in the 64 bit PCI slots available on dual boards? (I.E. are they backwards compatible?)

  2. #2
    Xtreme Tech Team Refugee Twisted's Avatar
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    i think you should be able to

  3. #3
    heezer7's Avatar
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    some yes some no. they have to have the same notches as the 64 bit cards
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  4. #4
    Inactive Super Quad Mod donny_paycheck's Avatar
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    Some are, some aren't. Look at the PCI card. If it has a notch near the side closest to the back of the case then yes, you can. If it has a notch on the side furthest from the back of the case, you can't.

    In short, if it fits, you should be alright.

    edit- heezer beat me to it
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  5. #5
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    What do you use in 64-bit slots? Raid controllers?
    Random posting and questions since June!

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    --------
    Last edited by A380; 11-23-13 at 02:07 PM.

  7. #7
    Inactive Super Quad Mod donny_paycheck's Avatar
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    RAID cards and a few graphics adapters are the only thing I can think of right now that use the slots.

    64-bit slots push 3.3v out of them. 32-bit slots usually use 5v. Some 32-bit PCI cards, hopefully always the ones that will fit them, are dual voltage and can handle both. PCI 2.1 (pre-1998) was the 5v standard that still lurks today. PCI 2.2 replaced it. The cards that can fit in both slots are PCI 2.2 cards.

    I hope I got that right...
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  8. #8
    heezer7's Avatar
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    oh and on my asus i connot have a 32 bit card in a 64 bit slot in jumperfree mode or it will not post. so you might find a weird fix like that if it doesn't work right away.
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  9. #9
    Member Spec_Ops2087's Avatar
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    I use my RAID controller in my 64bit slot...same as my USB 2.0 card



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  10. #10
    Just Another Retired Moderator Jon's Avatar
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    Originally posted by heezer7
    oh and on my asus i connot have a 32 bit card in a 64 bit slot in jumperfree mode or it will not post. so you might find a weird fix like that if it doesn't work right away.
    Did you try setting all the dip switches in the "off" position when using a 33MHz card in jumper-free mode in the 64/66 slots? It's supposed to work and has for many.

    I've got a SCSI RAID adapter that had the same problem but have yet to try it with all my dips set that way.

  11. #11
    Member cruc1fy's Avatar
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    I use my 32bit Gigabit NIC in one of my 64 bit slots. My transfer speeds went from ~150Mbps to ~700Mbps by moving the card to a 64bit slot.

  12. #12
    Member Henry Rollins II's Avatar
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    Re: 64-bit PCI slots....

    Originally posted by Caffinehog
    Can I use standard 32 bit PCI cards in the 64 bit PCI slots available on dual boards? (I.E. are they backwards compatible?)
    No. Some 32 bit pci cards are compatible with the 64 bit slot, but the slot itself is not backwards compatible.

    regards,
    Henry

  13. #13
    Member Henry Rollins II's Avatar
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    Originally posted by donny_paycheck
    RAID cards and a few graphics adapters are the only thing I can think of right now that use the slots.
    Harddisk controllers and network adapters are quite common in 64 bit pci, but video card?!? Which one?

    regards,
    Henry

  14. #14
    Member FunkDaMonkMan's Avatar
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    I have a pci geforce 2 mx200 and I use it in the 64 bit slot... it will play max payne perfectly... I haven't done a benchmark on it... but when I put it in a 32 bit slot.. it will barely.. barely run diablo 2.

    I'm guessing it uses the extra bandwith.

  15. #15
    Member Henry Rollins II's Avatar
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    My Gainward GF4 mx420 pci isn´t even physically compatible with the 64b slots.

    regards,
    Henry

  16. #16
    Senior Member kaltag's Avatar
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    I'm using my sound card and modem on the 64 bit slots and no probs yet
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  17. #17
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    I was about to make a thread about this. I got a Voodoo 4 4500 PCI, and in sandra, it says it is 64-bit capable. Is there a way to take advantage of this on my board? Also, it says the card doesnt suppost bus mastering!?! WTF?? I could have sworn that this card did...oh well..

  18. #18
    Member SP's Avatar
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    well, the first thing we have to realize is that being 64 bit or 32bit is only one of the characteristics of a PCI slot. There are a couple of others that are important also and these are signaling voltage levels (5v or 3.3v) and speed (33Mhz or 66Mhz). All of these things are factors but the signaling level is one of the more important issues when considering wether a card will work in a certain slot or not. The other 2 factors are usually less of an issue because the PCI slot will default back to work with the card. That is a 64bit PCI slot will default back to 32bits if the card installed in it is only a 32bit card and a 66Mhz PCI slot will default back to 33Mhz if a card that only supports 33Mhz operation is installed. When it comes to signaling level, however, a slot expects a card to support it's signaling level and it must do so or it either won't work or bad things will happen. To prevent this slots are keyed for either 3.3v or 5v signaling levels by the placement of keyway in the slot and the corresponding notch in the card. Thus if a card doesn't support the signaling level used by that slot you won't be able to insert it in the slot because the keyway won't line up with the notch in the card. A slot will always be keyed for one or the other (3.3v or 5V signaling level) and not both and thus will have the keyway placed in one of the 2 locations. Cards on the other hand can be keyed for either or both and thus either have a notch cut out to fit the 5v keyway, the 3.3v keyway, or they can have both notches cut out so as to fit into either a 3.3v or 5v slot. A card that has both notches cut out is a universial card and it will work in either a 3.3v or 5v slot.

    So, the answer to your question comes down to a couple more questions that you must answer and those are whether or not your 64bit slots are 3.3v slots or 5v slots and whether your 32bit card is a 5v only, 3.3v only or universially keyed card. Most of the newer 64bit slots like the ones you see on Xeon and AMD 760MPX boards are 66Mhz slots and a requirement of the PCI spec is that for 66Mhz operation 3.3v signaling levels must be used. That means those slots are 3.3v slots. So, in order to use a 32bit card in those slots it must support 3.3v signaling levels and be keyed appropriately either for 3.3v or universial. Many older 64bit slots, like the ones on old Intel boards and AMD760 boards, are 5v slots that only support 33Mhz operation. Those slots will accept a 5v only card or a universial card.

    A couple of things you might want to keep in mind however when using your 64bit slots is that if a 33Mhz card is installed in a slot that is 66Mhz capable not only does that slot itself default back to 33Mhz but also any other PCI slot that is on that same PCI bus or device that's on that same PCI bus must default back to 33Mhz operation. This includes onboard or system devices that may be connected to that same PCI bus. That means that installing a 33Mhz card in one of your PCI slots may slow down any other cards you install in the other 66Mhz slots if those slots are on the same PCI bus. I believe in the 760 MPX chipset all of the 64bit slots are on the same bus. Also to make matters worse I believe the southbridge used with the 760MPX connects to the northbridge through the 64bit 66Mhz PCI bus. So, if you install a 33Mhz PCI card in one of those slots it may slow down this connection and may in some situations impact system performance.

    Another thing to keep in mind is that while 3.3v signaling level is required for 66Mhz operation that doesn't mean that a card that supports 3.3v signaling level and is keyed as such or is keyed universially will support 66Mhz operation. Many cards that support 3.3v operation will only support 33Mhz operation. This isn't a problem as the card will still work in a 3.3v 66Mhz slot. It's just that the slot will default down to 33Mhz operation. Clock speed is determined by one of the lines on the PCI bus as described here.

    http://www.techfest.com/hardware/bus/pci.htm#4.8
    M66EN
    66MHZ Enable is left "open" or disconnected on add-in boards that support operation with a 66 MHz CLK, and grounded on add-in boards that support operation with only a 33 MHz CLK. 66 MHz systems place a pull-up resistor on this signal to detect if the add-in board is 66 MHz capable. If the signal is high, a CLK with a maximum frequency of 66 MHz is supplied. If it is low, a CLK with a maximum frequency of 33 MHz is supplied. 33 MHz systems attach this signal to ground. 66 MHz operation will take place only if both the system and the add-in board support it.
    Here are a couple of good links for more information about PCI slots, cards, keying, and which cards will work in which slots.

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

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

  19. #19
    Member SP's Avatar
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    I have a pci geforce 2 mx200 and I use it in the 64 bit slot... it will play max payne perfectly... I haven't done a benchmark on it... but when I put it in a 32 bit slot.. it will barely.. barely run diablo 2.

    I'm guessing it uses the extra bandwith.
    This doesn't necessarily mean the card is actually making use of the additional bandwidth of the slot. The reason you may be seeing this performance increase may be because the 64 bit PCI bus is a separate bus from your other PCI bus which your 32bit slots are on and most or all of your other devices are on that 32bit bus. That way your card has a separate PCI bus all to itself and doesn't have to share with everything else. This may also be what's happening in cruc1fys situation with his 32bit Gigabit Nic installed in his 64bit slot. In fact, I've seen some benchmarks where 32bit 33Mhz Gigabit ehternet adapters showed exactly the kind of performance increase he speaks of and this was the reason. In some of the benchmarks I've seen the adapters themselves were 32bit 33Mhz only cards. Yet when installed in the 64bit slots they showed an large performance increase. Thus it had to have been attributed to the fact that they were moved off of the PCI bus most of the other PCI cards were on and thus had a Bus all to themselves or at least mostly to themselves.

  20. #20
    Inactive Super Quad Mod donny_paycheck's Avatar
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    Originally posted by Henry Rollins II


    Harddisk controllers and network adapters are quite common in 64 bit pci, but video card?!? Which one?

    regards,
    Henry
    http://www.xilinx.com/pci/pci64_66.htm




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