26 Oct
2006
26 Oct
'06
11:12 a.m.
I have a qustion about powering the 8" disk drives I have connected to my disk
duplicating computer. Specifically, what is the "best" power on sequence?
The drives I use are the Tandon TM848-2E. It requires 24V @ 750mA and 5V @ 450 mA to
operate. Pretty easy so far.
I use an external power supply to power the drives. I want to add a relay powered by one
of the diskette drive lines from the standard PC supply to turn this power supply on.
Again, faily simple.
My question is what is the best order to turn things on. I've always turned the drive
on before powering up the PC, and turned the drive off after powering off the PC. Does
this really matter? I always make sure there is no disk in the drive before doing any
power cycling.
To simplify matters, I could always just put everything on one big switch on the mains.
You know, like using the power strip to power on/off.
Any opinions about this? Any suggestions?
Thanks,
Kelly
26 Oct
26 Oct
2:55 p.m.
On 26 Oct 2006 at 14:12, Kelly Leavitt wrote:
My question is what is the best order to turn things
on.
I've always turned the drive on before powering up the PC, and
turned the drive off after powering off the PC. Does this really
matter? I always make sure there is no disk in the drive before
doing any power cycling.
Given that signals on a floppy interface are active-low, I'm going to
venture that the sequence should be power to the CPU, then power to
the drive. This should prevent spurious drive head-loads, accidental
writes (even if you don't think you'll ever have a disk in the drive)
and other nicieites.
Similarly, powering down should be drive then CPU.
Or at least that's what seems reasonable.
Cheers,
Chuck
4:28 p.m.
On 26 Oct 2006 at 14:12, Kelly Leavitt wrote:
YEs, but any correctly-designed disk controller would use open-collector
drivers, which will appear as floating outputs when powered down.
My question is what is the best order to turn
things on.
I've always turned the drive on before powering up the PC, and
turned the drive off after powering off the PC. Does this really
matter? I always make sure there is no disk in the drive before
doing any power cycling.
Given that signals on a floppy interface are active-low, I'm going to
venture that the sequence should be power to the CPU, then power to the drive. This should prevent spurious drive
head-loads, accidental
writes (even if you don't think you'll ever have a disk in the drive)
and other nicieites.
Maybe. I don;t think it makes much difference.
I have an external drive box on my PC/XT, which contains the hard drives
(ST412-interface) and a couple of 3.5" floppies. In order to get the hard
drives up to speed before the machine tries to boot from them, I always
turn the drives on first, then the CPU box. And I have nevr had any
problems doing that.
-tony
4:51 p.m.
On 27 Oct 2006 at 0:28, Tony Duell wrote:
YEs, but any correctly-designed disk controller would
use open-collector
drivers, which will appear as floating outputs when powered down.
The OP asked if the sequencing might make a difference. Depending on
design, it might--and powering the CPU then the drive appears to be
safest. Perhaps I should have phrased it that way.
Cheers,
Chuck
8:40 p.m.
On Thursday 26 October 2006 19:51, Chuck Guzis wrote:
On 27 Oct 2006 at 0:28, Tony Duell wrote:
Of the two setups I have which use an external HD interfaced to a CP/M box,
my recollection is that it was done the other way around, you'd power up the
drive box first and shut it down last. Not sure why that was, though.
--
Member of the toughest, meanest, deadliest, most unrelenting -- and
ablest -- form of life in this section of space, ?a critter that can
be killed but can't be tamed. ?--Robert A. Heinlein, "The Puppet Masters"
-
Information is more dangerous than cannon to a society ruled by lies. --James
M Dakin
YEs, but any correctly-designed disk controller
would use open-collector
drivers, which will appear as floating outputs when powered down.
The OP asked if the sequencing might make a difference. Depending on
design, it might--and powering the CPU then the drive appears to be
safest. Perhaps I should have phrased it that way.
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