Seagate ST1500DL003 Set Features command, Aah, Enable read look-ahead read cache feature default

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4.3.2 Set Features command

This command controls the implementation of various features that the drive supports. When the drive receives this command, it sets BSY, checks the contents of the Features register, clears BSY and generates an interrupt. If the value in the register does not represent a feature that the drive supports, the command is aborted. Power-on default has the read look-ahead and write caching features enabled. The acceptable values for the Features register are defined as follows:

Table 9 Set Features command values

02H		Enable write cache (default).
03H		Set transfer mode (based on value in Sector Count register).
		Sector Count register values:
		00H Set PIO mode to default (PIO mode 2).
		01H Set PIO mode to default and disable IORDY (PIO mode 2).
		08H PIO mode 0
		09H PIO mode 1
		0AH PIO mode 2
		0BH PIO mode 3
		0CH PIO mode 4 (default)
		20H Multiword DMA mode 0
		21H Multiword DMA mode 1
		22H Multiword DMA mode 2
		40H Ultra DMA mode 0
		41H Ultra DMA mode 1
		42H Ultra DMA mode 2
		43H Ultra DMA mode 3
		44H Ultra DMA mode 4
		45H Ultra DMA mode 5
		46H Ultra DMA mode 6
10H		Enable use of SATA features
55H		Disable read look-ahead (read cache) feature.
82H		Disable write cache
90H		Disable use of SATA features
AAH		Enable read look-ahead (read cache) feature (default).
F1H		Report full capacity available
	Note		At power-on, or after a hardware or software reset, the default values of the features are as indicated above.

Barracuda Green SATA Product Manual, Rev. B 35