4.1BSD and bad sectoring

[Dave Martindale]

Your problem is probably that the bootloader ("boot" on the floppy)
has a disk driver which cannot handle bad sector forwarding, and your
"vmunix" has a bad sector in it.  You lose.  It should be possible to
add the bad sector forwarding to the standalone driver to fix this.

Once you get the system up, you probably have yet another problem.
(We have a SI 9800 controller, which I assume is at least as good as
the 9400 for bug fixes.)  When you do a write of many blocks to the disk
and one of the sectors being written to is bad, the controller aborts
the transfer showing BSE just as it's supposed to.  Unfortunately,
the driver determines which block got the error by looking at the RH780's
word count register to see how far along the transfer got, and the 9800
buffers up to 4 sectors of data in the controller.  Thus the calculated
bad sector number may be anywhere from 1 to 4 high, and the forwarding
calculation fails.  Does anyone have a fix for this?
So far this hasn't bothered us since we have flag-free packs, but SOMEDAY
it's going to get us....

	Dave Martindale, watcgl!dmmartindale