@Nuclear_Bob wrote:Your calculations about PSU power requirements is wrong.
When companies list the power requirements for graphics cards they assume a fully loaded system, E.g. a CPU (125w+), a number of optical drives, HDDs, fans, USB devices, etc. They also add a large cusion to allow for cheap PSUs that don't run to specs. Each 6 pin PCI-E power connector delivers 75 watts, each 8 pin delivers 150 watts. In this article, an R9 270 has a draw of less than 150 watts. A closer calculation of your system PSU requirements would be 150 x 2 (2 R9 270s) + 125 (CPU) = 425 Watts, this doesn't take into account other components though and you would have to add their draw as well. Also you want to run your PSU at less than 85% load, otherwise you can reduce its lifespan.
For your system I would suggest a minimum 650 watt PSU, or greater, this would allow 100 watts to other components such as HDDs and your MoBo, USB devices etc. + 15% to keep the load within 85%. 750+ would allow more headroom though. I run an R9 290 on a 650w Corsair TX, I can run the GPU and CPU at full load and not have any issues.
that would explain why i haven't shutdown or restarted during game play. my PSU is 900w, but either way, I plan to upgrade my PSU anyway.
to a modular design. and 90%+ platinum certified. as I plan on doing a hefty raid setup later in 2015 as well. total of about 15 drives (3 clusters).
to improve performance and redundancy.
Thank you for your input, by-the-way. 🙂
-update-
I just read the article you linked, and apparently we were both wrong.
the article states (down towards the bottom):
"AMD R9 270 Crossfire - On your average system the cards require you to have a 700 Watt power supply unit as minimum"
but I should still have a very small buffer at 900w, even with 125w draw from the cpu. (+/- 75w)
We aren't both wrong, the article says it draws 133 watts. Which as I said is less than 150. A 650 could run it but, a 700+ is what they suggest for headroom, which I did as well.
Just because a card uses two connectors, doesn't mean they put them under max load. Some cards will use two 6 pin connectors to even the load on PSUs with more than one rail, to keep the power draw clean.
Blfer, you should really upgrade your PSU, you are cutting it too close and probably starving your system. The 290s can spike up to 365+ watts, although you might not see instability, you might have reduced performance.
Nuclear_Bob wrote:
Blfer, you should really upgrade your PSU, you are cutting it too close and probably starving your system. The 290s can spike up to 365+ watts, although you might not see instability, you might have reduced performance.
No, as I said my model with 6 and 8 pin connector needs 300 watts max (75 + 150 + 75). That's tested. There are other 290s with two 8 pin connectors, which need max 375 watts (150 + 150 + 75).
This + my CPU, a Xeon e3-1231v3 + some other stuff like SSD, fans etc... is much lower than 480 watts. Even a 450 watts power supply would be enough.
Edit: The spikes to >360 watts in your linked test are too short to be relevant. Even an underpowered PSU can handle them.
