Weird issue in flashing BIOS of dual 5850

[polymorpher]

My first post

I have seen many people on this forum successfully flashed BIOS of multiple 5850 and got them both working at >1.1V, but I never had any luck even after spending hours on it.

Two Sapphire HD 5850 1GB cards, on PCI-E 2.0 x16@16 slot
Gigabyte 890FX UD7 Board
Thermaltake Lite 700W PSU

RBE + ATIflash works for each of them, but not both - when BIOS of both graphics cards are flashed to 950MHz/1.19V, one of them (shown as GPU 1, the one which my monitor is not plugged into) would then automatically drop to 400MHz core speed and 900MHz memory speed, voltage stays at 1.0V .

I have checked the power consumption of the entire system with a watt meter which the result stays stable at 340W (so there shouldn't be any power shortage). I have also tried different PCI-E slot for both graphic cards but never got both of them successfully working at  950MHz/1.19V. I have also tried a BIOS with lower core clock and same voltage level, but the problem remains.

In Ubuntu aticonfig can't even read temperature or set clock speed on the modded cards (both GPU0 and GPU1) and performance is dropped significantly (both cards seems to be working at 400MHz, mining rate is only around 150Mhz)


 

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[polymorpher]

Tried Sapphire Trixxx on Windows, same problem, overvolt does not apply to the second card.

I wonder how these people on the forum made it to 400MHash/s. Even with only one single card, my GPU simply freezes when I push it to 365MHash/s at 1.2V 925MHz core

[polymorpher]

Problem solved. It's just a tragedy of using cheap PSU. Unplugged one card and OCed the other to 1000MHz/1.25V, running at 398MHz, no problem at all.

[DBordello]

Good to know.  I was wondering what the symptoms of an undersized PSU were.

[lunano]

I wonder how these people on the forum made it to 400MHash/s. Even with only one single card, my GPU simply freezes when I push it to 365MHash/s at 1.2V 925MHz core

You sure it's worth it? I get 350MH/s on stock voltage with only 850MHz core. What's the stock voltage on your GPU?
What temperatures are you seeing?

[polymorpher]

I wonder how these people on the forum made it to 400MHash/s. Even with only one single card, my GPU simply freezes when I push it to 365MHash/s at 1.2V 925MHz core

You sure it's worth it? I get 350MH/s on stock voltage with only 850MHz core. What's the stock voltage on your GPU?
What temperatures are you seeing?

725MHz/1.088V

Income from increase in production rate is far greater than increase in cost of electricity, though the power consumption grows exponentially against voltage level and core speed. Temperature should be not a concern - @870MHz the temperature does not even exceed 55 C, with 90% fanspeed.

For now I changed them back to 1.088V/870MHz, waiting for my new 1200W PSU.

*More PSU are needed to compensate the increase in power consumption from GPU.  In my calculation I did not put that into consideration. To find the optimal strategy I have to collect more data.

[polymorpher]

Update: I was wrong. The problem was I set something wrong in RBE. Powerstate voltage should not be changed, otherwise GPU BIOS would treat it as invalid value - that's why one card dropped to 400MHz (and in fact it was both cards dropped to 400MHz. The "working" one was only an display error).

After everything was fixed, my cards could stay stable at 970MHz/1.25V, the whole system is draining 497W +-3W from wall. (1200W PSU, 80+ Silver)