Power for more than 4 IDE devices? HELP!

  • Thread starter Thread starter Helen McGee
  • Start date Start date
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Helen McGee

I have a 350 power supply (I think it's 350. might be 300, but is
definately 300 or 350. How would I check?). Currently I have an 80GB
and a 40Gb HD, and a CD burner and a Sony DRU DVD burner. I have 3
more hard drives I want to put in (Maxtor 160GB, 7200 RPM all), and
have a Maxtor ATA/133 PCI adaptor card to make my computer allow more
than 4 IDEs. But, no free power cables inside the comp. From a quick
look on google, it seems that there do exist splitters for the IDE
device power cables, but that there is some sort of issue about over
loading the power supply? How do I figure out if this will be a
problem, short of going ahead and doing it and seeing if the computer
goes up in flames? *silly smile* I have no idea what sort of power
usage the various thing in the computer have. I've also got an
ethernet card, a 56K modem, a USBv2 card, an AGP video card, and 2
fans plugged into the mobo, all of which I presume would have to be
taken into account when figuring out if I was going to be overloading
the power supply. Thanks so much for any help!
 
Helen McGee writes ...
I have a 350 power supply (I think it's 350. might be 300, [...]
[...] Currently I have an 80GB and a 40Gb HD, [...]
[...] is some sort of issue about over
loading the power supply? [...]
Click to expand...

You should investigate the jumpers associated with the drives to see if
one of them can spin-up, not at power=on, but later when it is queried for a
read/write. This allows the power drawn from the PS to be distributed over
time, and not to drawn all power at one time. Presumably, you should pick
the data drive and not the system drive ... but it may not matter, as the
system drive would simply spin-up a bit later in the boot sequence.
 
It really depends on the PSU and the mainboard. Some PSUs
seemingly have enough power, but then you discover that a)
your mainboard draws all its power on 12V and b) the 7
HDDs you put in draw 2A on spinup. Most PSUs cannot handle
this, since they deliver <20A or so on the 12V line.
In such a case a 550W PSU by one vender can be worse
than a 400W one by another vendor. It really depends on
the Amperes is can deliver on the +3.3V, +5V and +12V lines
and on the current your equipment draws on them.

I recently did a setup a little similar to your requirements
(7 HDDs, 1 CDROM, 1 Athlon XP mainboard) and found that an
Enermax EG465 (460W) PSU was fine. The model one step smaller
(EG365, 350W) should still be sufficient.

I would go with these minimal requirements (info can be
found on the PSU case):

+12V: >= 24A
+5V: >= 25A

The rest is less critical. Of course a somewhat smaller PSU
might still work, but for your setting you should do
some overengineering. You should also make sure airflow
is good (additional case fans) and that the HDDs are cooled.

As with regard to Y-cables (splitters) they are o.k.,
if you use them correctly, i.e. firmly plugged in
and no chaining. If you use several of them in series
you are likely to get problems. But one per PSU connector
is usually fine.

Regards,
Arno
 
First determine if you CPU draws on the 12V. I believe only the P4 does.

If not, your only concern the amount of power drawn on 12V by HDs and CD/DVD.
A rule of thumb is 20W for HDs and 30W for CDs. Your PSU could supply anywhere
from 120-160W at 12V. You have to look at the label on top.

Overloading the PSU often results in bad sectors or drive spin-down.

| I have a 350 power supply (I think it's 350. might be 300, but is
| definately 300 or 350. How would I check?). Currently I have an 80GB
| and a 40Gb HD, and a CD burner and a Sony DRU DVD burner. I have 3
| more hard drives I want to put in (Maxtor 160GB, 7200 RPM all), and
| have a Maxtor ATA/133 PCI adaptor card to make my computer allow more
| than 4 IDEs. But, no free power cables inside the comp. From a quick
| look on google, it seems that there do exist splitters for the IDE
| device power cables, but that there is some sort of issue about over
| loading the power supply? How do I figure out if this will be a
| problem, short of going ahead and doing it and seeing if the computer
| goes up in flames? *silly smile* I have no idea what sort of power
| usage the various thing in the computer have. I've also got an
| ethernet card, a 56K modem, a USBv2 card, an AGP video card, and 2
| fans plugged into the mobo, all of which I presume would have to be
| taken into account when figuring out if I was going to be overloading
| the power supply. Thanks so much for any help!
 
CPU=AMD Athlon XP 2000+, Mobo=Asus A7s333. So, I dunno if it draws on
12v. Eric, you said only P4, but did you mean only of the pentiums, or
only of all CPUs on market today?
About setting jumpers to have drives spin up on read/write instead of
power on, I'd very much like this. Where would I find this out? I
looked through the book that came with the HDs, but didn't see
anything about it. They are all maxtors, and fairly recent ones. The
only thing I can find on the maxtor website is about Cylinder
Limitation, which I know isn't what is being refered to. Is it a
jumper on the mobo rather than on the HD? Or where?
Thanks for the info on the Y Splitters. I wasn't planning to chain
them, was planning to put one Y splitter on each of the 4 PSU
connecters.
 
Arno Wagner said:
It really depends on the PSU and the mainboard. Some PSUs
seemingly have enough power, but then you discover that a)
your mainboard draws all its power
Click to expand...
on 12V
Click to expand...

But at a substantially lower amperage than it would on 5V.
and b) the 7 HDDs
Click to expand...

What 7 HDD?
you put in draw 2A on spinup.
Click to expand...

That is 2A maximum, for a short while (less than 10 sec).
You could probably call that peak.
Most PSUs cannot handle this, since they deliver <20A or so on the 12V line.
Click to expand...

Less than 20 is fine as long as the remaining headroom is 9-10 Amps.
In such a case a 550W PSU by one vender can be worse
than a 400W one by another vendor.
Click to expand...

And not necessarily because of that single amperage per supply line spec.
It really depends on the Amperes is can deliver on the +3.3V, +5V and
+12V lines
Click to expand...

If that is how they are configured. Specifications can be conservative
in several ways. There may be some extra headroom available on some
lines when not all supply lines are used to their maximum specification.
and on the current your equipment draws on them.

I recently did a setup a little similar to your requirements
(7 HDDs, 1 CDROM, 1 Athlon XP mainboard) and found that an
Enermax EG465 (460W) PSU was fine. The model one step smaller
(EG365, 350W) should still be sufficient.

I would go with these minimal requirements (info can be
found on the PSU case):

+12V: >= 24A
+5V: >= 25A
Click to expand...

Without any further reasoning, that is just a number that you picked.
 
4.5 Power Requirements
MODE 12V (MA) 5V (MA) POWER (W)
Spin-up (peak) 1619.3 870.6 23.2
Seek 661.3 857.9 12.2
Read/Write 410.8 669.9 8.3
Idle 343.8 667.2 11.2
Standby 36.6 123.9 1.1
Sleep 36.9 122.7 1.1

Source:
DiamondMax Plus9 60/80/120/160/200GB AT
Product Manual
April 22, 2003
Part Number: 1877
Rev a

The motheboard does not power the CPU from the +12 volt line, so if
the power supply can provide > 10 amps at 12 volts, it should be okay.
 
Helen McGee writes ...
I have a 350 power supply (I think it's 350. might be 300, [...]
[...] Currently I have an 80GB and a 40Gb HD, [...]
[...] is some sort of issue about over
loading the power supply? [...]
Click to expand...

You should investigate the jumpers associated with the drives to see if
one of them can spin-up, not at power=on, but later when it is queried for a
read/write. This allows the power drawn from the PS to be distributed over
time, and not to drawn all power at one time. Presumably, you should pick
the data drive and not the system drive ... but it may not matter, as the
system drive would simply spin-up a bit later in the boot sequence.
Click to expand...

I have a device which is labeled "disk sequencing". It connects in line with the power
to a hard drive and delays its power on for several seconds.


-Barry
========
Web page: http://members.optusnet.com.au/~barry.og
Atheist, radio scanner, LIPD information.
Voicemail/fax number +14136227640
 
Barry OGrady said:
I have a device which is labeled "disk sequencing".
It connects in line with the power to a hard drive
and delays its power on for several seconds.
Click to expand...


Did you make it or did you buy it? If you bought
it, where did you buy it?

Does the boot procedure wait until the hard
drives(s) is/are up to speed before proceeding?


*TimDaniels*
 
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