View Full Version : undervolting hd 4850 to run on 200w psu
geofrancis
09-30-2009, 05:05 PM
i have recently upgraded my server in my morex 669 itx case the problem is it only has a 200w psu and im starting to reach the limits of it with what i have installed in it.
phenom 9150e 65w undervolted to 1.05v @ 1.8ghz
J&W Mitx 780g htpc board
4gb ddr2 800 (2x ddr2 800 so-dimms)
5 x 3.5" sata hard drives
2x usb dvd-rw's
at the moment im using the 780g onboard graphics but i have a hd4850 that i want to install in it but i dont think that the power supply is up to the job because i hooked a kill-a-watt up to the computer and its saying its using 138w with prime 95 running and 122w with prime 95 + furmark so now my problem is i only have 60 or so watts to play with.
as far as i know a hd 4850 uses about 110W full load but how far can this graphics card be undervolted at stock speeds and underclocked and how much power will it save?
if that fails i have an external ac to 12v 120w adapter that i could wire up to power the graphics card via the pci-e power cable but will that be enough?
pic of the case
http://i44.tinypic.com/ifwx9j.jpg
Jakalwarrior
10-01-2009, 07:36 AM
What are you planning on doing with it? My card is clocked to 125mhz and low voltage for 2d usage, it probably sips power at those settings. I'm sure you can shave some off of the 3d load number but I still can't see a 200 watt PSU living long if you play a demanding game. You really don't have 60 watts to play with. Running a PSU at max wattage is like holding your car at the red line.
saaya
10-01-2009, 11:33 AM
dont be so cheap and get a new psu :P
undervolting alone wont do the trick, undervolting plus underclocking might work...
but then why did you upgrade the vga to begin with ;)
geofrancis
10-03-2009, 07:15 AM
i cannot upgrade the power supply because its designed for that case alone and i sold the hd4850 so i could get a 4650 that would sip power but the idiot that bought it couldn't get it working so i had to refund him. but when i got it back i realized i could just squeeze it in if i ran it of an external 12v source plugged into the pci-e power connector and used a pci-e ribbon cabled riser to move the card one slot along.
largon
10-04-2009, 03:22 AM
To lower GPU voltage, solder a 100kΩ variable resistor set at maximum resistance between the blue dots in the following pic:
97872
geofrancis
10-05-2009, 09:37 AM
i can lower the gpu voltage in software with ati tray tools or with radeon bios editor im just wondering has anyone measured the power consumption stock vs underclocked?
RejZoR
10-05-2009, 09:57 PM
Forget it. My card died because of undervolting. Besides, what's the point of having HD4850, if you're clocking it down to Radeon x1600 performance?
zanzabar
10-05-2009, 10:09 PM
why didnt u go for a 4770
geofrancis
10-06-2009, 05:29 AM
like i said at the start i already tried to sell the card on ebay so i could get a 4650 but the guy that bought it was an idiot and sent it back.
now can i get an external 12v supply and wire it in parralell into the 12v line of the case power supply so that instead of just powering the graphics card pci-e power connector it helps power the rest of the computer also. i assume this wont cause any problems. i was thinking of something like thishttp://cgi.ebay.co.uk/ws/eBayISAPI.dll?ViewItem&Item=390098680031&Category=58288&_trkparms=algo%3DLVI%26its%3DI%26otn%3D1
Jakalwarrior
10-06-2009, 01:48 PM
Why not shoehorn in a different PSU for the whole system if you are going to go through that kind of trouble They make some 300-500 watt microatx PSUs.
geofrancis
10-07-2009, 06:49 PM
i am thinking of using a 12v 120w external brick hooked up to the 12v line on the internal 200w psu to help it.
would that work ok as long as it it was in parallel ?
Glow9
10-07-2009, 07:11 PM
does it have onboard video why do u need a 4850 for a server?
geofrancis
10-08-2009, 05:24 PM
origionaly i had 2 computers a server (this one ) and my gaming rig. then i moved house and now i have got a pre pay electric meter that costs a fortune so i sold my main gaming rig and upgraded my server to a quadcore/4gb ram/hd4850 so i can game on it.
now about my last question can you hook an external 12v source into the 12v line of the powersupply to help it or will it screw something up?
Hell Hound
10-14-2009, 05:40 PM
Well I have a dedicated psu for my vga's it uses a 4pin dongle from my main psu ,and it also has its own power cord,it also fits in my 5.25 bay just get a external dvd drive and use a dedicated gpu psu.:up: