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calvin6666

(IDE/ATA standard) Addressing?

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In "memory" world, 3 bits can address 8 data to be accessed.....But, I dont understand why only 3 bits (ie. DA[2:0]) can handle the Gbytes-level hard disk addressing? Shouldn't hard disk need more address lines to deal with the storage mechnism (why noly 3 bits can read/write Gbytes data storage in physical hard disk)??

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In "memory" world, 3 bits can address 8 data to be accessed.....But, I dont understand why only 3 bits (ie. DA[2:0]) can handle the Gbytes-level hard disk addressing? Shouldn't hard disk need more address lines to deal with the storage mechnism (why noly 3 bits can read/write Gbytes data storage in physical hard disk)??

Logical block addressing is a linear translation of existing CHS values

LBA = (C * Number_of_Heads + H) * Sectors_per_Track) + S - 1

It doesn't refer to cylender/head/sector, but instead addresses each sector (N+1 where N is the sector). This allows you to have more than 1,024 cylinders, 16 heads and 63 sectors (1,032,191 sectors total for CHS). LBA is 48 bits, so that's 2^48th sectors (281474976710656 sectors).

Can someone check to see if my memory is correct?

Thank you for your time,

Frank Russo

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DA[2:0] selects one of 8 register addresses in the controller logic. Each of these register addresses may be used to actually read/write several internal registers. 48 bit LBA uses 3 of these addresses, where the first write sets LBA(47:24) and the second write ("most recently written") sets LBA(23:0).

This is pretty convoluted, but remember the roots of the ATA interface (ST506) date back 25 years.

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