I'm no computer expert, but I'm pretty sure all TTL logic works with 5v, and CMOS works from 3.3v to 5....VoxLupus wrote:I think that you are a little too optimistic with that PSU Fluke.
You must bear in mind that not all of those 500 W are available to the CPU and GPU.
That is powered by the 12 V rail, which for the CX500 is rated at 34 Amps.
12 V*34 A=408 Watts
For the 390, that is a an overhead of 7% for the power available to the GPU and CPU in those bench marking applications (assuming the other components are negligible), and this is assuming that the relatively low-quality PSU is operating at peak performance. I am also not sure if those power draws take into account factory over clocks. Having such a small margin may cause issues with the stability of the system, especially since some applications may lead to greater power consumption than the ones tested here.
I don't know about you but that is a little to close for me to feel comfortable with. I think you will be hard pressed to find many people recommending a 500 W PSU for a R9 390.
Here is a forum post I found relating specifically to this question:
http://www.tomshardware.com/answers/id- ... u-390.html
I think that one of the reasons that the difference in power consumption is not significant in the benchmarks you listed (80 Watts as apposed to the expected 150 Watts) is that the 390 is typically CPU bound due to bad driver optimization. AMD is addressing these issues and along with DX12 I have a feeling that these will lead to improved performance as well as an increase in power consumption.
I know I have oversimplified some things, and while you are right that the 500 W will probably work, I think the potential issues it may lead to will not be worth it. The 970 would be the safer option by far.
And on all the microcontrollers/processors I've worked with, this was true...
Another thing I might add. The i5 in my laptop only uses 5 watts... When I'm REALLY using it. It goes up to around 11W...
I KNOW that this won't be the same for desktops. Laptops are designed to use less power...
If it happens to run on 12v, it probably has a regulation circuit inside, but that would be inefficient, and generate unnecessary heat...
My advice.
'Yote. If you can spare the cash. I'd go for the bigger PSU. But it depends on what you want to do...
It leaves a open margin for future upgrades, and it's something that will always be compatible with new hardware...(up untill they bring out new connectors...)
I've never even had a desktop. So I don't know all this overclocking and GPU's and stuff...
But they've been arguing about the PSU so long... You're probably reading this from your new PC aren't you?