How Do You work Out How Much Power You Need...

Aunty Em

Aunty Em

Well-Known Member
... to run a given PC?

I've read that you should never load your PSU to full capacity, so is there a set formula for working out how much wattage you actually need according to the devices in the PC?
 
On intels...
I use
PII - 200-250w at-atx
PIII 250-300
P4-cel 300-400
P4 350-400

I'll get you some spec on those power supplies.;)
 
I was actually reading this article but it doesn't mention other stuff like fans and lights etc.

How PC Power Supplies Work - page 3

According to this I will need 155W without including the CPU or lights and fans (if I use the upper value).

1x mobo 30
1x agp 30
1x pci 5
1x floppy 5
1x net card 4
256 ram 20 (40 later)
Hdd 11 (15 later)
2x CD Drives 50
________________
Total 150

So my 400W should be adequate.
 
I try to stay at least 50% under the psu limit. But I run a lot of scsi, so startup is a beast.
 
i run a XP 1700+ on a 250W, most my other cpus run on 350-550W Psus, brand matters alot, this FSP group psu with the 1700+ actually started and ran My Pentium 4 @ 3.1Ghz without any stability errors, whilst a 400W Macron (lol) failed to even start it, heck it even failed to start my XP 2100+ rig. Bands i use are generally Enermax, FSP Group, Sparkle (which i believe is FSP group as i bought a sparkle and they sent an FSP group psu, which i was pleased with anyhow) and Antec.
 
I have a 250 watt on a P4-1600
Get at least 400 watts, then you won't need to worry about not having enough power.
 
I usually have a 300W psu on this computer, but I put the 400W in to make sure it's running OK. I just want to make sure it's enough for what I intend. I'll be putting the mobo and ram in here initially(they were sent out yestrday so should be here by wednesday at the latest) with my present processor and cards to make sure everythings OK with them, then when I get the rest of the bits at the end of the month (case, lights, fans, floppy, heatsink and processor) I'll be transfering them to the new case. :)

Once that's running OK I'll get a new HDD, get a cheap soundcard and retrieve my Geforce from Katie's computer for this one and get her a cheap video card for her comp and a new HDD later in the year.

That way I'll have 2 comps - the faster one running as it should and this one for over-clocking and anything else I'd like to try. I'll be able to duel boot them both and try the different OS's before I finally decide which one(s) I prefer. It will also give me the opportunity to learn to network all three, both wired and wireless.
 
I had a 400w Sparkle, I paid close to a hundred bucks for. It puked after a year. I replaced it with a generic 400w for $22.00 including shipping....it's still going after about a year.:headbang:
 
Mine's a Mercury and cheap @ £23.50 inc s&h, though in my local comp shop it was priced at £35. Let's hope it does the same. :)
 
I don't even think mine has a name, it's so generic :D

:headbang: Three cheers for cheeeeep-o power supply's
 
Wired network is soooo much easier. I have used both and wireless is a pain in the arse
 
I'm using a $15 Codegen 350 watt on my XP2000+ and it's stable. The psu was AMD recommended for up to a XP2000.

The 400 watt psu that came with the case fluctuated.
 
I'm using a Codegen 350 watt on on my p4-2.53gig too.
I always rewire the fans on these codegens though.
They have the running too slow. Straight wire it and it works great.:cool:

I agree with Justin on the brand thing, partially.
I think the output specs. are most important, but the brand
also insures that it will run for more than 30 days. (usually)
 
I got an Antec 400w POS

When it gets over about 68° in the room, it starts refusing to operate when the CPU is at high load. It'll shut itself off.

The fan in it died, so I had to ghetto-rig a fan in there and plug it up to one of its own molex connectors :tardbang:
 
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