Power for two 5850

[swissmate]

So I'm expanding my rig with a new 5850.
Will my PSU(600 watts and 3 years old) give enough energy for two 5850?

Computer specs:
Intel Quad Core 2.4Ghz
4Gb Ram
2 HDD
2 Amd Sapphire 5850
Psu 600 watts

[1715382604]

1715382604

[1715382604]

1715382604

[check_status]

What are the PSU specs; How many rails; what brand; how old is the PSU?
If it is sold on Newegg provide a link.
What motherboard will they be run on?
Do you have a wattage meter like, Kill-A-Watt brand?

In the mean time, here are some helpful articles.

The 5850 has a maximum board power of 151W to 179W, depending on model.
http://www.guru3d.com/article/radeon-hd-5850-review-crossfire/2

Energy consumption

We'll now show you some tests we have done on overall power consumption of the PC. Looking at it from a performance versus wattage point of view, the power consumption is pretty good for a product of this caliber, according to ATI the 5850 has a TDP of 151 Watts.

....

Keep that in mind. Our normal system power consumption is much higher than your average system.

    System in IDLE = 168 Watts
    System with GPU in FULL Stress = 348 Watts
    (5850 consumption = 180 Watts)

Recommended Power Supply

So here's my power supply recommendation:

Radeon HD 5850

    The card requires you to have a 500 Watt power supply unit at minimum if you use it in a high-end system. That power supply needs to have (in total accumulated) at least 40 Amps available on the +12 volts rails.

Radeon HD 5850 CrossfireX

    A second card requires you to add another 170 Watts. You need a 650+ Watt power supply unit if you use it in a high-end system. That power supply needs to have (in total accumulated) at least 55~60 Amps available on the +12 volts rails. 

For each card that you add, add another 200 Watts as a safety margin.

http://www.guru3d.com/article/radeon-hd-5850-review-crossfire/9

Single GPU 5850

    System in IDLE = 157 Watts
    System with GPU in FULL Stress = 334 Watts
    Difference (GPU load) = 184 Watt (official reference TDP = 170W)

http://www.guru3d.com/article/his-radeon-5850-icooler-v-turbo-review/6

Both models did draw 180 Watts+, but in mining power consumption can be less depending on how you clock your cards so working with a wattage meter will provide much better info.

[swissmate]

thanks for the info.
i'm not sure which model it is but the motherboard is an asus p5k SE
i'll try them both with that psu and if it seems not stable ill be getting one with higher wattage.

[gyverlb]

You'll probably be fine using 150MHz for the memory clock, 1V for the GPUs instead of 1.088V and between 800 and 850MHz for the GPUs' clock.
With a 80+ silver PSU at near peak efficiency my 5850s with such configuration add around 100W to my rig (real power draw at the wall socket) so should use ~90W from the PSU.

At stock voltage, 150MHz memory, ~930MHz they draw ~125W at the wall socket here. So it should be fine too but might not be as profitable (depends on your kWh cost, PSU efficiency, ...).

[swissmate]

You'll probably be fine using 150MHz for the memory clock, 1V for the GPUs instead of 1.088V and between 800 and 850MHz for the GPUs' clock.
With a 80+ silver PSU at near peak efficiency my 5850s with such configuration add around 100W to my rig (real power draw at the wall socket) so should use ~90W from the PSU.

At stock voltage, 150MHz memory, ~930MHz they draw ~125W at the wall socket here. So it should be fine too but might not be as profitable (depends on your kWh cost, PSU efficiency, ...).

Those values seem very nice for me
Thanks

[David_Benz]

Should be fine bro.

They take about 150watts each and if you run them at stock voltage, 840/300 you will get a good 350mhash and 600w PSU should do fine.  But you will wear it out soon.

[swissmate]

I'm afraid to tell that it's not enough wattage for the two 5850

[Dargo]

I'm afraid to tell that it's not enough wattage for the two 5850

Bummer - but you can undervolt your cards for right now until you get another PSU. 5850s undervolt very nicely. At 0.95, mine pull about 90w and I can get a bit over 300 Mh/s. They are easy to undervolt with cgminer (in both linux and windows).

[ssateneth]

you probably have a multirail card, which is bad and makes it seem like your 600w power supply is only a 300w, because it has power locked to certain places, such as if you have 3 rails, atx connector might be on one rail and cpu power might be on another rail, leaving only one rail left to power all your hard drives and video cards and fans. it would be impossible to use locked-out power from the atx/cpu power unless you spliced the connector physically to allow connecting stuff to it (i.e. voiding your warranty)

[swissmate]

Thanks for the info
Didn't really know about that "multirail" problem

[aqrulesms]

Thanks for the info
Didn't really know about that "multirail" problem

http://www.newegg.com/Product/Product.aspx?Item=N82E16817171053&Tpk=cooler%20master%20750w

That should suffice your needs.

I have that exact same PSU and it can run a 7970 that pulls 250w at stock and the 150.  At the same time I have a pretty expensive CPU since this used to be my gaming PC, yet it provides enough power to everything.