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The motherboard manual doesn't say. It's an AsRock H61M/U3S3, updated to latest BIOS ROM.

Any idea what it is or if I should turn it on?


I tried turning it off: system doesn't boot.

So despite being a "Legacy" option, (and off by default, I think) I need it on to boot my brand new SATA3 Samsung 840 Pro SSD. Weird.

So it's not a compatibility option for older hardware. Anyone else have any ideas?

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Did you try it? – daxlerod Jul 9 '13 at 12:49
Please provide more detail on the problem your attempting to solve? – Ramhound Jul 9 '13 at 13:08

It may be a ROM provided by the chipset to emulate IDE access, which you'd need if you plan to run DOS on that system or other legacy OS that doesn't support SATA.

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As far as im aware this is a "compatibility" mode that allows older hard drives to be used on newer chipsets. If your current setup is working with it off, you need not worry about it or turn it on .

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