18 Jun
2009
18 Jun
'09
7:05 a.m.
On 17/06/2009 16:34, Johnny Billquist wrote:
It's actually worse. The write enable signal
apparently always gets to
both drives no matter what else you are doing. So when you write to one
drive, the other will also start writing, even if the head is moving
right at that time. I've had to recover an RD53 which was destroyed that
way. (Salvage as much data as I could, and then reformat the drive.)
That won't happen unless both drives are also selected. Having the
write enable signal go to both drives at the same time is normal in
ST412 systems, and indeed all the signals go to all the drives at the
same time in such systems.
The funny thing is that DEC actually do write in the
documentation that
it is not permissible to have two hard drives in a BA23, but that note
is not so easy to find, and if you don't have the documentation, it even
easier to assume that you can, since you do have connectors for two drives.
The DEC information actually says that it's because of the power
requirements.
I believe it's a hardware "bug", which
can't be fixed without cutting
wires, and adding new ones. But maybe someone knows better here?
Mine works, and I've not cut any wires.
--
Pete Peter Turnbull
Network Manager
University of York