Step rate on 2nd hard drive (UNIX-PC)?

[Lenny Tropiano]

In article <1666 at naucse.UUCP> sbw at naucse.UUCP (Steve Wampler) writes:
|>Sigh.  I had forgotten that iv cann't be used to change the VHB
|>on a drive with >1024 cylinders.  Is there another (easy) way
|>to change the step-rate on such a drive?  Will the extended
|>diagnostics let me do it without munging the existing file
|>system?
|>
...
I made a program that would patch iv(1M) to allow >1024 cylinders.
It was posted to unix-pc.sources a while back, if you never received
it, let me know.  Of course IT'S UNTESTED.  I don't think it would hurt
your disk, but I couldn't guarantee.  Backups are of course suggested.

|>I suppose I could open /dev/rfp010 and read in the VHB myself,
|>but I don't have a layout of the VHB.  (Since the step-rate
|>change only takes effect on reboots, this would work, wouldn't it?)

The layout for the VHB is in /usr/include/sys/gdisk.h:


/*	volume home block on disk	*/
struct vhbd {
	uint	magic;		/* S4 disk format code */
	int	chksum;		/* adjustment so that the 32 bit sum starting
				   from magic for 512 bytes sums to -1 */
	struct	gdswprt dsk;	/* specific description of this disk */
	...

You could write a program that opened up /dev/rfp010, read in struct vhbd
and then change vhb.dsk.step = 14 and write it back out (basically what
iv(1M) does...) 

Hope this helps,
Lenny
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