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What is an Enhanced BIOS?

April 26, 2017BIOS Enhanced

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What is an Enhanced BIOS?

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An Enhanced BIOS is a BIOS that makes it possible to use hard disks exceeding the (in)famous 504MB (528 million bytes) barrier with DOS/Windows. The origin of this limit is the disk geometry (cylinders, heads, sectors) supported by the combination of an IDE drive and the BIOS’ software interface. Both IDE and the BIOS are capable of supporting huge disks, but their combined limitations conspire to restrict the useful capacity to 504MB. An Enhanced BIOS circumvents this by using a different geometry when talking to the drive than when talking to the software. What happens in between is called ‘translation’. For example, if your drive has 1500 cylinders and 16 heads, a translating BIOS will make programs think that the drive has 750 cylinders and 32 heads. Unfortunately there are several flavors of translating BIOSes. The de facto standard is the Microsoft/IBM ‘INT 13 Extensions’ document; Phoenix has presented a superset of this in their Enhanced BIOS specification. Phoenix, AMI and Awa