Andre Hedrick wrote:
> That is a legacy bit from ATA-2 but it is one of those things you cannot
> get rid of :-(
in ANSI X3.279-1996, "AT Attachment Interface with Extensions (ATA-2)",
Approved September 11, 1996 , control register bit 3-7 are reserved.
However ANSI X3.221-1994, "AT Attachment Interface for Disk Drives",
Approved May 12, 1994, bit3 is "1" and bits 4-7 are "x".
No further explanation.
How far back must we go, to get the sense ?
> struct {
> unsigned bit0 : 1;
> unsigned nIEN : 1; /* device INTRQ to host */
> unsigned SRST : 1; /* host soft reset bit */
> unsigned bit3 : 1; /* ATA-2 thingy */
> unsigned reserved456 : 3;
> unsigned HOB : 1; /* 48-bit address ordering */
> } control_t;
>
> once I add-in the real def of bit3 then I will not
> need to look it up again.
bit3: 0: drive has 1-8 heads
1: drive has more than 8 heads
(From old MFM/RLL times. In ATA-1 bit3 is set to 1.
See also
http://www.win.tue.nl/~aeb/linux/hdtypes/hdtypes-2.html
.)
Andries
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