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Why 300W power is insufficient ??

Last response: in Motherboards
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May 27, 2002 3:19:07 AM

Hi all,

I've got a question, probably you may have the one as well:

I don't understand why the 200W(sometimes even 300W) PSU is not enough for the moden general system:

For the general system,

AMD XP ( approx 65W)
Cooling Fans (Total appox 20W)
Hard Drive (approx. 20W)
CD ROM (approx. 20W)
Graphics Card (approx. 30W)
Mother board ( approx. 30W)

(note: the power of CRT is supplied seperately)

I just listed some parts and approx power wastage here. the overall system power should be under 200W in most cases. at least 250W PSU will be enough for most systems. but why some many people complain even the 300W PSU is insufficient??
May 27, 2002 3:49:48 AM

its more than Wattage.
Its about current draw.
modern computer components, particularly the cpu and graphics card, draw alot of current.
in athlon systems the cpu draws it from the 5v line.

if the PSU cannot supply sufficient current close to the specified 5v u get lockups and random reboots.

also, not every 300W psu is the same. Quality varies FAR too much in my opinion, and the wattage rating of the PSU is also misleading.
for example, if you take a 300W enermax unit, arguably the best PSU maker out there, it will supply much higher currents on each of the rails compared to a cheap generic lightweight PSU.
ive seen one instance where the 300W enermax had better current ratings than a 350W generic!!!

so you really dont need a high wattage psu for your average system, just a quality brand. (although having some headroom is always a good idea)

another important point. cheap & nasty PSU's are MUCH more likely to fail as they are running much closer to their operational limits + cheap components.


<font color=red>MABACITISS</font color=red>: Movement Against Boasting About CPU Idle Temps & Idle System Stability!
May 27, 2002 3:52:25 AM

I don't know. It think I heard it may have to do with the way the voltage and ampage is distributed.

I have a 350 watt power supply on my case (I think it is an Eagle brand or something), and I can run my system fine (though I don't know if something like a 400 or 500W would improve performance for me).

I have a 266A by Abit with built RAID but no other integrated features.

1800+ XP

512 PC 2100

20GB, 7200, ATA-100

GF 3 Ti 200 128MB

SB Live X-Gamer 5.1

10/100Mb NIC

One CD-ROM and burner (both high speed)

And two 80x80mm ball bearing case fans.

I imagine I am probably almost using my PS up to the max with all this.

My 17" CRT monitor is on a separate plug in the wall (as you mentioned), and so are my speakers.

I occasionally plug my scanner in too.

I really don't know. But I've heard Enermax makes some really good PS' They have a 450W one my local computer store is selling for $100

Also, I have a Valcano 7+ (7100 RPM) fan cooling my XP, and my northbridge has a fan thanks to Abit.
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May 27, 2002 5:23:57 AM

It's because power supply manufacturers LIE when they rate their power supplies these days. Often that big number represents a peak capacity that will only work for a few seconds or less, and not even with a stable voltage output.

What's the frequency, Kenneth?
May 27, 2002 5:19:11 PM

20 watts for cooling fans? thats a bit much dont you think? each fan takes maybe 4 watts at the most, two case fans, one cpu fan, one psu fan, thats a max of 16 watts, i bet its more like 12 watts.

how do you shoot the devil in the back? what happens if you miss? -verbal
May 27, 2002 6:44:38 PM

i don't know, let's see, 4 case fans, 1 cup fan, 1 graphics card fan, 1 northbridge fan....it looks like it adds up... =) 4x4 1x4 1x4 1x4...er....20 looks ok to me =)
May 27, 2002 8:24:39 PM

bah humbug!
forgot the chipset fan and gpu fan.

how do you shoot the devil in the back? what happens if you miss? -verbal
May 28, 2002 12:18:24 AM

It depends on the brand of the PSU. Most cheap noname 250-300W PSUs are not enough for modern systems. If you have more than 2 drives (DVD/CD-RW/HDD ect.) or you´re using a modern graphics card, you should get a PSU from a wellknown company like Antec, Enermax or Codegen.
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