"Arthur" said:
Good day !
I'm running a P4PE P4 2.53 Ghz 512 DDR with :
-2 IDE hard drives
-1 Radeon 7500 (without power connector)
-1 Dvd
-1 CDRW
-1 Floppy
-1 USB Cable modem, 1 USB Webcam, and 1 parallel printer
Can i safely add a third IDE hard drive to my config (i have an extra IDE
connector on the Mobo) without buying a new power supply ? Is 350 W enough ?
Thank you !
Arthur
From the P4 2 to 3.06GHz datasheet, a 2.53/533/512KB processor draws
52.5 amps at 1.5 volts. When converted from +12V, this is 6.56 amps.
Correcting for 80% Vcore conversion efficiency raises the estimate to
8.2 amps max. Counting disk drives, there are three spindles spinning
all the time, at 0.5 amps each. You could include another 0.5 to spin
the DVD or the CDRW. Allow an amp for 3 big fans to cool the computer.
The total is 11.2 amps from the +12V supply. Check the label on the
supply and see if it can deliver that much.
When the computer first starts, the three drives spin up simultaneously.
This draws 2 amps per drive per spinup. But while the drives are spinning
up, the processor is not running flat out. So, the two tend to cancel.
A margin of an amp or two on the above estimate should handle it.
As for the other supply rails, generally supplies are so generous on
the +3.3 and +5, it isn't worth wasting time trying to compute them.
The best method, is to go to the Intel website, as Intel manufactures
motherboards - find an Intel motherboard that uses the 845PE Northbridge,
and download the manual. Intel motherboard manuals are unique, in that
they give low and high estimates for power consumption on their motherboard.
Those numbers can be used as a gross estimate of +3.3 and +5 consumption.
Then, of course, you have to find numbers for all the other stuff plugged
into the computer that draws +3.3V and +5V.
Your video card is reasonably low power, so shouldn't need too much power
thrown into an estimate. If the graphics chip only has a passive heatsink,
it probably isn't burning more than 5 watts.
Computing power estimate is based on not only the total consumption,
but is more focused on what the output capabilities of each rail on the
supply happen to be. The label on the power supply will tell you what
the maximum current is. You would want the +12V rail to be able to supply
at least 11.2 amps, and I would be happier to see 13 or 14 amps of output
capability, to give some margin and avoid the "mushy" zone, where the
supply voltage is starting to drop as the current approaches the max.
BTW - There are web sites with info on computing power requirements,
but like me, they will overestimate what is needed. However, their
estimates will convince you that a 550W supply is needed, which is
definitely not the case. A system like you've got will be drawing
roughly 160 watts from the wall when it is busy. So, as long as your
350W supply puts its juice on the rails that are most heavily loaded,
it will work.
I just took delivery of a 2.6GHz/800/512KB processor and 865G based
motherboard, and it draws 0.55 amps from the wall idling with one
disk drive in WinXP. When running 3DMark2001SE Demo, it draws 1.0 amps
at 120V during the nature scene. Say we call this 120W, and then allow
an extra 10W per idling disk drive, 160W should cover the extra drives
plus the better graphics you've got compared to this board.
(Note: This job would be so easy if computer products were required
by law to state their power consumption
))
HTH,
Paul
