64-bit PCI works in a 32-bit slot?

Discussion in 'OT Technology' started by deusexaethera, May 16, 2006.

  1. deusexaethera

    deusexaethera OT Supporter

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    I plugged a Dell PercRAID card with a 64-bit connector into a 32-bit PCI slot today -- effectively letting the extra piece of the 64-bit connector dangle freely -- just to see what would happen. As I expected, Windows reported that the device couldn't initialize itself. But then I installed the PercRAID driver for the hell of it, and the card reported that it was working fine.

    ?!?

    I haven't connected any SCSI drives to it yet, because I don't have any that I can afford to erase and/or destroy with my little experiment, so I don't know if the card could actually transfer usable data without being connected to a 64-bit PCI slot. I had assumed, though I could be wrong, that if the card were connected improperly that the computer would hang or at least report an error, but it's not doing that; I used the computer all day with no ill effects. For the record, I do have 64-bit slots on my motherboard at work, but I specifically used a 32-bit slot just to see what would happen.

    Can 64-bit PCI cards plug into 32-bit PCI slots and still work? Or did my experiment reveal a fluke in the design of this particular card and/or my particular motherboard?
     
  2. Mikey D

    Mikey D New Member

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    Found this on a google search.

    66MHz slots are keyed so that 33MHz cards cannot be used in them, nor can 66MHz cards be placed in 33MHz slots. 33MHz 32-bit cards are keyed so that the cards will physically fit in both 32-bit and 64-bit slots. Typically, compliant 64-bit slots will run any 32-bit card. 33MHz 64-bit slots cards are keyed so that the cards will physically fit in 64-bit slots. 64-bit cards will also fit into 32-bit slots as long as there is enough physical space behind the trailing edge of the slot. Some 64-bit cards will work in 32-bit slots, albeit with some loss in functionality.
     
  3. deusexaethera

    deusexaethera OT Supporter

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    Ah, so it's set up the same way the various flavors of AGP are; if it doesn't fit, it definitely won't work. Well, this particular card has notches cut into its 64-bit connector such that it can plug into a 64-bit slot AND a 32-bit slot. I had hoped the "no-fit, no-function" standard would hold up, but standards are only as reliable as the companies that use it. It seems my curiosity was rewarded this time.

    Next test is where I plug in some disks and hope for the best.
     
  4. DAN513

    DAN513 OT Supporter

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    as long as it's a newer motherboard, you should be fine.
     
  5. EvilSS

    EvilSS New Member

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    A lot of the RAID cards were designed to work in both (albeit not as fast in the 32 bit slot) so they didn't have to create two parts for the server lines back in the day when 64bit slots were only found in the bigger boxes.
     
  6. deusexaethera

    deusexaethera OT Supporter

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    Well, "not as fast" isn't really so bad when it means I get to use a $900 PercRAID in a computer that could really use the extra fault-protection of RAID and access speed of SCSI, instead of letting it sit in a drawer until one of the PercRAIDS in service dies, which will probably never happen. Thanks for the info.
     
  7. EvilSS

    EvilSS New Member

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    Check the manual to be sure but I'm willing to bet it is a supported config. Unless you are maxing out the drives and completely shitting on the cache you won't notice the difference at all.
     
  8. deusexaethera

    deusexaethera OT Supporter

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    Heh. I've been looking for the manual for hours. I should go back to Excite.com -- Google and I just don't get along, I dunno why.
     
  9. rsxm5

    rsxm5 OT Supporter

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    Don't know for sure about the PercRAID cards, but Adaptec SCSI cards (the 29160 and 29320 series cards) are 64-bit, and work perfectly in 32-bit slots.
     
  10. deusexaethera

    deusexaethera OT Supporter

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    Too bad the 29XXX's don't support hardware RAID, though. I swear we have enough of them at work to give them away to starving orphans.
     
  11. rsxm5

    rsxm5 OT Supporter

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    Hook me up with a 29320? :x:
    I have a PC that needs and upgrade.
     
  12. ShapeShifterz

    ShapeShifterz Longtime Lurker

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    I have a perc4e/si running in a normal PCI slot, so yes, 64 bit cards work in 32 bit slots.
     

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