17 Jun
2009
17 Jun
'09
3:34 p.m.
Ethan Dicks <ethan.dicks at gmail.com> wrote:
On Sun, Jun 14, 2009 at 4:14 AM, Johnny Billquist
<bqt at softjar.se> 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.)
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.
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?
>
> ...and if you wanted to use more than one hard drive
> on the RQDX3 you also need the RQDXE, since the BA23 distribution board is buggy,
and
> can't actually connect two hard drives, even though you have two connections.
> I think it's worth pointing out that people should never even try connecting two
hard drives in a BA23.
> You'll definitely wreck whatever contents you have on the disks if you try.
I thought there was a way to do it, but you had to start moving drive
select jumpers around and it was still easy to get a double-select and
trash your contents. I remember trying to put a pair of RD52s or an RD53
and an RD52 on one
machine 20+ years ago. I also remember not succeeding. Clearly an
RQDXE would have made the job simpler (possible?), but we didn't have
one handy.
The RQDXE will definitely do the trick. If your "not succeeding" just
went as far as you didn't get it to work, without trashing the conents
of a drive, you were lucky.
Johnny
--
Johnny Billquist || "I'm on a bus
|| on a psychedelic trip
email: bqt at softjar.se || Reading murder books
pdp is alive! || tryin' to stay hip" - B. Idol
18 Jun
18 Jun
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
5678
days inactive
5679
days old
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