2 Jun
2011
2 Jun
'11
12:20 a.m.
On 01/06/2011 18:23, Johnny Billquist wrote:
Yeah. Nothing mythical about the 6-button panel. Glad
to see that I'm
not the only one thinking so.
Although some manuals do mention that you should only use one hard drive
in a BA23 (eg the Maintenance Manual) I've seen several systems --
including mine -- do so with no problem. I've never seen a problem with
Write Gate, nor would I expect to. Like all other ST412-type
interfaces, the M9058 distribution card has the same write gate signal
wired to all the 34-pin HDD connectors in parallel. In fact the /only/
control signals not wired strictly in parallel on those connectors are
some of the drive selects.
What I do know is that the docs say you must draw no more than 7A from
the 12V supply in a BA23, and one RD51 takes 4.5A. So 2 x RD51 would
overload it. I believe that's the only restriction, because putting a
second RD5x in a BA23C expansion box, connected via an RQDXE, was
supported -- and AFAIR the RQDXE doesn't do anything clever with the
control or status signals.
--
Pete Peter Turnbull
Network Manager
University of York
I remember_trying_ to put two hard disks in one
machine for quick
disk-to-disk copies. I have a fuzzy memory that it didn't work for
me, but I don't remember whacking either drive to the point that they
didn't work when returned to their former homes.
As far as I know, the BA23 backplane distribution panel can *not* be
used for two disk drives. I know there is a DEC note/article about this
not working. You need the external distribution board for the RQDX3 to
use two drives. If you use the BA23 backplane distribution panel with
two harddisk drives, you have a high chance of corrupting both disks.
(If I remember right, the write gate signal somehow goes to both disks,
no matter what, which cause the disk to possibly start writing when the
disk is seeking, for example. Very bad.)