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  1. #1
    New ROGer Array
    Join Date
    Apr 2012

    Help - Problem with SAS Host Bus Adapter

    I'm having problems with the BIOS recognizing my LSISAS9212-4i4e host bus adapter. I've got a Maximus IV Extreme-Z motherboard with dual Radeon HD6970 GPUs running in crossfire mode. The GPUs occupy PCIe 2.0 x16/8_1 and PCIe 2.0x8_3 slots as per the Maximus user's guide. The problem I'm having is that the host bus adapter (HBA) is only recognized if plugged into PCIe 2.0 x16/8_1 (not good because that's where the GPU should go) or in PCIe 2.0x16_4 (but this slot is blocked by the GPU in PCIe 2.0x8_3).

    Any advice about how to proceed? Will a different HBA work better?

    Also, is it OK to plug my two GPUs into PCIe2.0x16/8_1 and PCIe2.0x16_2? This would free up PCIe2.0x16_4 which would no longer be blocked by the large GPUs? Note that the Maximus user manual hints that performance will suffer if I configure my GPUs like this? How bad will performance suffer?

    Thanks advance for any help.

  2. #2
    ROG Guru: Yellow Belt Array
    Join Date
    Mar 2012

    It looks to me like pci-e x8_3 is split into x16_2 and x16_4 with the NF200 splitter chip if you use either of those slots, effectively disabling the x8_3 slot.
    It is possible to run both gfx cards on ports x16_2 and x16_4 and put the SAS card in x16_1. This will result in a lower pci-e lane count between your gfx cards and the cpu, but most reviews indicate that the every day effect is slim to none. So in your case this is what I'd try.

  3. #3
    ROG Guru: Grand Master Array HiVizMan's Avatar
    Join Date
    Dec 2011

    You will hardly notice any loss of performance if you do place the second gpu into a different slot. Only if you benchmark will you be able to see the very slight hit in performance.
    To help us help you - please provide as much information about your system and the problem as possible.

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