Answer
According to the datasheet of Intel 5 series chipset, "it can support up to two different images on different display devices". Therefore, the H55H-I V1.1 does not support 3 outputs of onboard HDMI,DVI,& D-sub working at the same time. It allows you to run any 2 of the onboard graphics simultaneously as below configuration based on Intel's spec.
D-sub + DVI + HDMI
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Not support
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D-sub + DVI
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OK
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D-sub + HDMI
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OK
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DVI + HDMI
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OK
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