GPU for 12V 18A 300W power supply

Bucic · July 1, 2014

What are the most powerful GPUs for a PSU with only 18A on its 12V line? AMD preferred.

Please note:

- with my low-power system (AMD APU 65W) the PSU is capable of running AMD 6850, watt-wise

- 'buy a new PSU' is not helpful

Specifications of the PSU:

http://www.bequiet.com/en/powersupply/325

Abburo · July 1, 2014

P=UxI

U=12V

I=18A

P= 216 W

However, video cards needs multiple voltages, so you have to repeat the above calculation for each of it. Moreover, in this case 216W is an absolute maximum but you always have to consider 80% of power to be on the safe side.

PS: 300W is by far too low for an gaming PC. Don't forget 50-100W draw by CPU, HDD, motherboard, soundcard... all these generate power consumption that must be add to GPU of course.

Edited July 1, 2014 by Abburo

Bucic · July 1, 2014

Is there a chart that lists GPUs by their power consumption (not p.c. of the whole test systems)? Also, power consumption aside, AFAIK there are per-GPU manufacturer's recommendations regarding the supply current (amperage).

I've started the topic because there are various opinions on the subject. Some say 'the manufacturer recommended 20A' while others say 'you can calculate it from the power consumption', neither of them stating sources

e.g. http://www.tomshardware.co.uk/forum/303750-33-amps-6850

Edited July 1, 2014 by Bucic

Abburo · July 1, 2014

I don't know about any consolidated chart with power consumption, but you can start from a search like this:

http://www.bing.com/images/search?q=amd+gpu+power+consumption&FORM=HDRSC2#a

Thick8 · July 1, 2014

Plug all fo your variables into this calculator then start swapping out GPUs till you find the best one that meets your power criteria.

http://extreme.outervision.com/psucalculatorlite.jsp

SkateZilla · July 1, 2014

What are the most powerful GPUs for a PSU with only 18A on its 12V line? AMD preferred.
Please note:
- with my low-power system (AMD APU 65W) the PSU is capable of running AMD 6850, watt-wise
- 'buy a new PSU' is not helpful

Specifications of the PSU:
http://www.bequiet.com/en/powersupply/325

what are you specs (which APU?)

you can prolly use AMD Dual GPU with the APU.

NRG-Vampire · July 1, 2014

sure, you dont want this answer but you must buy a new psu

300w is too weak (maybe enough if you dont want to run dcsw) :smilewink:

Buzzles · July 1, 2014

I second NRG. Not the answer you want, but a new PSU is in order if you want to upgrade your GPU.

Personally, I wouldn't go for less than 600w as most dedicated gpus are asking for well over 200w, as shown above (12v x 18amp = 216w).

Bonus fact: Going big with PSU is always better. Being able to supply more power than required will mean the PSU runs cooler and in a more stable fashion. Maxxing a PSU is never a good idea.

Bucic · July 1, 2014

Thanks guys! Please hold on. I *do* consider buying a new PSU, just wanted to know, what I could squeeze from this one. I've learned some interesting stuff today and I'm going to share it as my small contribution. Obviously point No 1 is going to be "Wattage is only a part of GPU power requirements".

In the meantime:

- the system is not for DCSW; at least not intended ;)

- Llano A4-3400 paired with 1600 MHz RAM

- I've never considered dual (+APU) graphics. Seemed like another mumbo to me :)

Rhinox · July 2, 2014

... "Wattage is only a part of GPU power requirements"... :)

Exactly. Apart from stability/quality and similar issues, one more topic is power distribution. 300W PSU can not "move" power freerly from 3.3V-branch to 5V or 12V. There are certain limits, and these are sometimes defined as "combined power" (+5V & +3.3).

BTW, concerning PCI-express based cards you can check GPU-card design to estimate upper limit of power it can theoretically draw: from pcie 16x slot GPU can draw ~75W (iirc, 10W from 3.3V, rest from 12V). Then there are additional 6-pin power connectors (~75W) and/or 8-pin power connectors (~150W).