I just wanted to share my optimization for these cards.
As you probably know new Gigabyte cards come with locked voltage at 1.25V and stock clocks at 1000Mhz GPU, 1250Mhz memory. This makes cards run hot and power consumption is high.
I have 3x 7950 setup and system took ~950W and it was really hard to keep them under 75C at stock clocks with 85% fan speed. Hashes were (avg) 610kh/s per card.
Later I found out that there is an older official BIOS (F43), which has lower voltage lock and lower clocks. So I tried it and flashed the cards.
Here is how I did it:UPDATE 1:HDMI port will stop working with F43 BIOS! So you will have to use DP or DVI to connect your monitor.UPDATE 2:There are new cards with FT0 BIOS which won't let you flash official F43 BIOS over it.
Please check this thread for further info: http://www.overclock.net/t/1313813/new-bios-update-for-gigabyte-hd7950/790 So check your current BIOS version before you proceed any further!
Thanks Mattzees for this update! (https://forum.litecoin.net/index.php/topic,4317.0.html
1. Download F43 Bios: http://www.gigabyte.com/products/product-page.aspx?pid=4121&dl=1#bios
2. Download atiflash: http://www.techpowerup.com/downloads/2230/ATIFlash%204.07.html
3. you need DOS bootable USB drive. I used this tutorial: http://www.sevenforums.com/tutorials/46707-ms-dos-bootable-flash-drive-create.html
4. put F43 Bios and ati flash to USB drive
5. Turn off the computer
6. Put BIOS Switch on the GPU to number 1 http://www.jagatreview.com/wp-content/uploads/2012/02/gigabyte-amd-hd-7950-dualbios-switch.jpg
If anything goes wrong you can just put switch back to number 2 and you have factory default BIOS.
7. Boot with USB drive to DOS
8. Check the version of the current BIOS
atiflash -aiIf you have FT0 BIOS then you can not use F43 BIOS!
9. Flash to F43 BIOS version:
atiflash -p 0 xxxxxx.F43
10. Check BIOS version on the card
atiflash -ai 0
Now my cards are at 900/1250 @ 1.090V stock.
I use this cgminer config:
1155/1420 core/memory clock speed
Thread Concurrency 24000
Threads per gpu 1
lookup gap 2
Power Limit 20%
setx GPU_MAX_ALLOC_PERCENT 100
setx GPU_USE_SYNC_OBJECTS 1
cgminer --thread-concurrency 24000 --lookup-gap 2 --gpu-engine 1155 --gpu-memclock 1420 --gpu-powertune 20 -w 256 -I 19 -g 1
I am getting (avg) 2005kh/s
with all three cards, so around 668 kh/s
per card without HW errors and low stales on stratum pool.
Temperatures are around 66°C with 66% fan speed and power consumption dropped for ~40W per card.
You will still need an open rig with extra fan(s) to get decent temperatures!
Here is pic of my rig:http://shrani.si/f/Y/sP/2rk1ed85/photo-1-small.jpg
F43 BIOS was total winner in all aspects - power, performance and temperatures.
So if you have the same card, I strongly recommend you to do the same.
Here is my latest screenshot of cgminer:
Have a great day!
If you appreciate this and it is saving you money you can donate some coins
P.S.: you can also try TC 16384 and 21712. It works even better for some. I got 60 kh/s more in total with 16384 but I also got around 5 HW errors/day, so it seems 24000 is optimal for my setup.EDIT 1:
I've updated GPU clock, cgminer image and some typos.EDIT 2:qtpZ%5%LlJNvb3Sd found out that setting memory Clock to 1250 takes away only around 1-2 kh/s but saves you more power so I think 1420 is not worth it.Disclaimer: I am taking no responsibility for any damage you might have by following these instructions. There is always some risk involved when flashing the BIOS, so you must know what you are doing.