Upgrading my system, PSU help?



Hello there!

So, I'm upgrading my current PC with some new parts and I would love to know how big my PSU will need to be for all this to run perfectly.

Alright so first of I have to mention that I already have an HIS Radeon HD6870, the one I have cannot be bought anymore, I think. The "art" on the card is a sword along with the text "HIS".

Moving on to the parts,
Gigabyte GA-990FXA-UD5
Corsair 4GB (1x4096MB) CL9 1600Mhz VENGEANCE <- I will have two of these
XFX Radeon HD 6870 <- Remember, this will be in Crossfire with another HD6870 by HIS
AMD Phenom II X4 965 @ 3.4GHz NOT Black Edition so it's at 140W. Will upgrade to Bulldozer FX when it comes out.
Corsair H50
I currently have this HDD, will upgrade later on.

I will also have a USB keyboard, USB mouse, Iomega 2TB external HDD, Logitech G35 Headset, 2xUSB flash drives and occasionally I will have my phone USB cabel.

This is the case I'll be using, IN WIN Dragon Rider.
With the case I will have 2x120mm, 1x120mm LED and one 220mm LED fan + the H50 120mm fan.

I think that pretty much covers what I'll be using. So my questions are, how big of a PSU will I need and do you think the H50 will fit on an AM3+ motherboard?
I've tried using a PSU wattage calculator tool but I'm no good when it comes to that so I would really love some help in this.

Thanks in advance! :)


Radeon HD 6870 x1
On your average system the card requires you to have a 500 Watt power supply unit.

Radeon HD 6870 x2
A second card requires you to add another ~150 Watts. You need a 700 Watt power supply unit.

Measured power consumption one 6870 card

System in IDLE = 173W
System Wattage with GPU in FULL Stress = 295W
Difference (GPU load) = 122 W
Add average IDLE wattage ~ 19W (ATI specified)
Subjective obtained GPU power consumption = ~ 141 Watts

Measured power consumption two 6870 cards

System in IDLE = 184W
System Wattage with GPU in FULL Stress = 421W
Difference (GPU load) = 237W
Add average IDLE wattage x2 ~ 19W (ATI specified)
Subjective obtained GPU power consumption = ~ 275 Watts


IN SHORT: 700w would be plenty for Crossfire 6870's

Look for brands such as; Corsair, XFX, SeaSonic, Enermax, Antec

At minimum look for 80 PLUS BRONZE rated. Silver/Gold is better but also comes at a price.
Modular PSU is recommended for easier cable management.


@AdrianPerry is that 700W for everything included? The HDD, USB things, the DVD/CD thing, LED fans (they seem to take quite a lot).

I don't know how much a USB headset, mouse and keyboard takes up, but can't be much can it?


I just tried it out and if you or someone else could just quickly go through it and check by the given information above if I did everything right. I would be very grateful for that :)

System Type: 1 physical CPU
Motherboard: Regular - Desktop
CPU: AMD Phenom II X4 965 3400 MHz Deneb
CPU Utilization (TDP): 100% TDP
RAM: 2 Sticks DDR3 SDRAM
Video Card: AMD Radeon HD 6870
Video Type: Crossfire

Regular SATA: 1 HDD
DVD/CDRW Combo Drive: 1 Drive
USB: 7 Devices
IEEE-1394 FireWire: 1 Device
Regular: 5 Fans 120mm;
LED: 1 Fan 120mm; 1 Fan 250mm;
Pump Relay: 1 Relay
Keyboard and mouse: Yes
System Load: 100 %
Capacitor Aging (+ W %): 30 %

Minimum PSU Wattage: 719 Watts
Recommended Wattage: 769 Watts

I include my external HDD, keyboard, mouse, flashdrive and phone charger in the USB list. I'm unsure about my motherboard, if it's Regular or High-End. Also not sure about the "Pump Relay" thing. I didn't find the Corsair H50 in the liquid cooling set so I just added one just in case. Also sett it to 100% load, just in case :p.

Other than me being a little unsure it seems alright.


Generally i do "high-end desktop"

Just calc'd your build with "high-end desktop" and got 631w recommended. Even with capacitor ageing, 700w is enough, 750w if you really want to be safe


Alright so with "High-End Desktop" I get,

Minimum PSU Wattage: 744 W
Recommended PSU Wattage: 794

Now, just one question, my HDD is at 7200RPMs but it's still a regular SATA and not a high RPM SATA?

Again I included my external HDD, keyboard, mouse and other stuff in the USB Device list. I'm not even sure if my external HDD drains anything from the PSU because it has it's own power cable. Not quite sure about the keyboard and mouse though, they can't require much wattage at all. It also says "Other Hardware: Keyboard & Mouse (included)".

Just calc'd your build with "high-end desktop" and got 631w recommended
What did you do to get such a low one? :O Can you post the print thingy?


Keyboard and mouse aren't included in USB devices (they are added automatically).

SATA HDD I included as a High-RPM, again just to be safe (theres a good chance High-RPM is classed as 10,000 - but nevermind, slower will use less)

If your external HDD is powered externally this also doesnt need to be included in USB devices.

The reason your getting such high wattage suggestions is because your putting capacitor ageing % on. You only need to apply more than 10% if your PC is going to be constantly running 24/7. Most PSU's are rated for 100,000hours so very little capacitor ageing will occur. Having system useage at 100% will also never ever happen during general use. The only time your going to be running at 100% load right across your build on both GPU's and your CPU is if your running some super intensive benchmarking tools such as prime95.


100,000 hours?! That's like 11 years :O
I just put 100% load to be sure.

But this is great news, I guess I can keep using my Corsair TX850W :D


Oh yeah without a doubt. Corsair 850w is MORE THAN ENOUGH for your build :D and a good quality PSU too.

900w is the recommended for SLI GTX 580's
800w is the recommended for CrossFire 6970's so your more than covered.

Lets see what the manufacturer says for the 6870:


500 Watt or greater power supply with two 75W 6-pin PCI Express® power connectors recommended (600 Watt and four 6-pin connectors for AMD CrossFireX™ technology in dual mode)

Putting your system into a PSU calculator.....

Using the above, and all of your components, I get 496 watts draw and 565 watts Recommended ... that was assuming a decent quality PSU w/ 15% capacitor aging.

A decent (read 9.5 jonnyguru performance rating) 650 watter is therefore more than enough. A XFX Core Edition if you don't OC, a 750 Core Edition if ya do would be my recommendation.

$70 650 watts http://www.newegg.com/Product/Product.aspx?Item=N82E16817207014

$85 750 watts http://www.newegg.com/Product/Product.aspx?Item=N82E16817207015

Both get 9.5 performance ratings from jonnyguru but are generlly less expensive than comparable units with the same rating.


Aug 26, 2011
i would recommend the seasonic 750watt fully modular psu its awesome but it it 170$ at newegg but dont get a cheap psu


Well I already have a Corsair TX850W so I don't need a new one.
Sorry to dig this up but I read on a site that the Vengeance memories doesn't work on all motherboards so, does anyone know if these CORSAIR Vengeance 8GB (2 x 4GB) 240-Pin DDR3 SDRAM DDR3 1600 (PC3 12800) will work on this motherboard Gigabyte GA-990FXA-UD5?

I haven't bought new RAMs in quite a long time and my knowledge is very limited when it comes to compatibility and things like this :p

Thanks in advance!
Look at the Memory Support List here:


Well I found "CMZ8GX3M2A1600C9" which are the memories I linked so it should work :D

Thank you :)!