View Full Version : Power supply for XFX 8800GTS 640MB XXX Edition

07-27-07, 03:59 AM
Greetings to all forum members,

I have recently purchased an XFX GF 8800GTS 640MB XXX Edition (600Mhz core) graphics accelerator.

The writing on the box says :
NVIDIA MINIMUM POWER SUPPLY REQUIREMENTS - Minimum 400W or greater power supply

This makes me a little bit confused. I intend to use an ANTEC EARTHWATTS 500W PSU. Will it do the job?

The system also consists an INTEL Q6600 CPU, a P35 based mainboard, 2x1GB RAM, one hard drive and one optical drive (no SLI).

Thanks in advance. I would appreciate a response from someone who has this card (or similar) and knows for sure.

P.S. One of my considerations for choosing an NVIDIA based accelerator over ATI was lower power consumption, so having to spend more money on the PSU now would make me unpleased.

07-27-07, 04:17 AM
If your PSU has 26A or higher on the 12V rail(s), then it'll handle your system perfectly well. I would recommend at least 30A though so your PSU isn't near full load all the time - this extends life and reduces heat.

I notice that your PSU has dual 12V rails with a combined maximum of 34A (17A each) which should theoretically be enough. Unfortunately, PSUs are supposed to have one 12V rail dedicated solely to the CPU which leaves the other rail to power your graphics card AND other components in the case of dual rails.

I'd imagine your PSU is seriously borderline for this. 17A is just barely enough to power a pre-overclocked 8800GTS, plus hard drives, fans, optical drives, etc...

I would recommend you get a PSU with either one strong or 3+ 12V rails just to be on the safe side. In any case, your current PSU's life would probably take a hit for the worse if you loaded it with this system and it worked because one of the 12V rails may be pushed to 90%+ of it's 17A limit.

07-27-07, 07:16 AM
Thanks for your reply.

I've made a list of possible PSUs within my budget. It is ordered by price from cheapest to most expensive :

1. ENERMAX LIBERTY 400W - two 12V rails of 20A each = 40A total
2. ANTEC TRUEPOWER TRIO 430W - three 12V rails of 16A each = 48A total
3. ANTEC NEO HE 430W - three 12V rails of 16A each = 48A total
4. ENERMAX LIBERTY 500W - two 12V rails of 22A each = 44A total
5. OCZ GAMEXSTREAM 600W - four(!) 12V rails of 18A each = 72A total
6. CORSAIR HX 520W - three 12V rails of 18A each = 54A total
7. ANTEC NEO HE 500W - three 12V rails of 17A each = 51A total
8. ANTEC TRUEPOWER TRIO 550W - three 12V rails of 18A each = 54A total

Please help me choose the cheapest PSU whish is also adequate for my system, as specified above. Any suggestion, note or remark will be greatly appreciated.

Thanks again.

Joe Public
07-27-07, 07:25 AM
You can't add up the values of all the rails to calculate the combined amperage, that will be incorrect. That's just what you can load each rail max with, but not all of them at the same time. (and sometimes the PSUs don't even have separate rails in practice). Anyway, if you multiply the amperage values you state in the post above with 12V, you get a watt value. But you end up with more than the PSU is rated for. For instance, the 400W Enermax. 12V x 40A = 480W. But it's only 400W. Doesn't really make sense, does it? :)

The actual value is usually lower. For instance, the Corsair HX520 can deliver 40A on the 12V rail and the HX620W delivers 50A. That's 480W on the 12V for the 520W and 600W on the 12V rail for the 620W. Which makes more sense.

You should rather find out what the rated wattage output on the 12V for the PSUs in question.

07-27-07, 07:55 AM
7. ANTEC NEO HE 500W - three 12V rails of 17A each = 51A total
This is the one I'm using right now. I haven't had any problems. Check my Sig for my PC specs.

07-27-07, 08:12 AM

The one component people tend to ignore is there psu, save a few bux, and so on.which is not the way to go.

I just did a new build, and granted i am running 8800gtx sli and a 1 gig oc on a q6600, so I was willing to spend a few extra bux on my psu, but it ended up that i didnt have to.

I found a pc power and cooling 750 watt silencer quad for 169 on theyre website.They even did a custom wirning harness for nothing, and changed they sleeeving color.Great service, and its poweriing my rig awesomly with outstanding voltages
Still on sale


Its not a 1k unit, but there is still headroom, and leaves room for upgrading to next gen stuff.

Not saying that this is the end all psu, but its damn good and very very quiet.Just check out my rig.

Joe Public
07-27-07, 08:24 AM

Gives an idea of what a high-end gaming system may draw from the PSU. 442W for an overclocked, SLI loaded Core 2 Quad system. One is pretty much secure with a 6-700W PSU.

07-27-07, 08:29 AM
i think you will be borderline with that PSU... why not try it out and see if it works?... some people always recommend crazy PSU's... it helps in the long run to have a strong PSU since you won't need to upgrade it so often...

07-27-07, 11:59 AM
People are right in saying you can't generally just add up the currents on the 12V rails because it usually results in a power greater than the PSU can supply. The CORSAIR HX 520W PSU for example has a 40A limit on the 12V rails, so 12V1 may supply 16A, 12V2 supplies 16A but that means 12V3 can only supply 8A.

If you want my recommendation on which power supply to go for, it would definitely be the Corsair HX520 because I've seen nothing but glowing reviews about it. It also has 'current sharing', meaning if the current on one rail exceeds it's limit, other rails will divert current to compensate. I don't think any other PSU in that list offers that ability. Unfortunately, you pay a price premium for this.

My second recommendation would be the OCZ gameXstream 600W - the reviews I've seen of it say it's very good and it should easily be able to power your system. I was actually going to get this PSU myself for my Q6600, 8800GTX system.

07-27-07, 12:05 PM
I am running all the stuff in my sig of a 400watt power supply. No problems so far although I will be getting a Corsair 520 watt psu at the end of the month for peace of mind. I think the power supply is whats limiting my overclock.

Joe Public
07-27-07, 12:42 PM
One of the reasons I chose a Corsair 620W was because of the fact that it doesn't have current limiters for each rail. The "power sharing" thing is just semantics and actually means it has one big 50A rail.

07-27-07, 01:00 PM
Thank you all for your help.

I have decided to stay with the Earthwatts 500W for the time being. After reading some reviews I'm pretty confident it is sufficient.

Let's hope this is not a mistake.

07-27-07, 01:05 PM
If you choose to go for a new one, the Corsair 520w is on Buy.com for 79.99 AR or 69.99 with Google checkout, which is a great price for this PSU. The rebate ends on 7/31.

07-27-07, 01:13 PM
I am running all the stuff in my sig of a 400watt power supply. No problems so far although I will be getting a Corsair 520 watt psu at the end of the month for peace of mind. I think the power supply is whats limiting my overclock.
all that on 400W? wow... is that even a 24pin power supply or just an old 20pin?... also check the voltages with a program... should give you an idea if you need to upgrade

07-27-07, 02:36 PM
That guy probably stopped checking this thread but , Id get a thermaltake 250w thing If I were him.
Or if I was me.