Hi forum,

I just want to tell you some experience with mining on a system. Just in case you are planing a system like that.
Here is the system relevant hardware list:

AMD Phenom(tm) II X6 1055T Processor
Chieftec APS-1000C (1000W / 900W for pciE)
OCZ Vertex2 E 2,5" SSD 60 GB
19" 4HU

XFX 2GB HD5970
XFX 4GB HD6990

overall price around 1600 EUR (January 2011)

I am using bitcoin-0.3.21 and m0mchil-poclbm-06cf386 on a Linux ubuntu 2.6.35-24-generic. I don't like ubuntu
but the installation of the AMD (GPU) SDK simply works. I lunch 4 times the poclbm.py in parallel because you
can not specify multiple devices. I think using dual gpu cards - nice and easy - is still not really supported by the
SDK - but from my coding experience with it - it works to start 4 kernels on 4 gpus but this will decrease the over
all computation speed - at least for me...

Just a quick note about overclocking the gpus. I decided not to do that simply because (I may be naive) I hope
the card will have a longer lifetime :-) I did some test with like 100-150mhz on the core and this increased the
fan noise "exp" :-)

Adapter 1 - ATI Radeon HD 5900 Series
Current Clocks :    550           1000
Current Peak :      725           1000
Configurable Peak Range : [550-1000]     [1000-1500]
GPU load :    100%

Adapter 2 - same

Adapter 3 - AMD Radeon HD 6990
Current Clocks :    830           1250
Current Peak :      830           1250
Configurable Peak Range : [500-1200]     [1250-1500]
GPU load :    99%

Adapter 4 - same


Speed results (running 48h+):

26/05/2011 X, 194437 khash/s < HD5970
26/05/2011 X, 194408 khash/s
26/05/2011 X, 340399 khash/s < HD6990
26/05/2011 X, 340302 khash/s


My experience:

I think this - "oh the complexity increases so far because of the gaming gpu kids" - is very overrated.
1. If you do not have a dedicated system for processing it is in my opinion impossible to use or (play with the system
2. My room temperature (20sm) increased like 5 degree (C) - air moisture down
3. It is impossible to sleep next to system - i am a nerd i am used to sleep next to case-less mb only systems (like 10 y ago) -
   but - if you are a computer guy - the noise of my system can be compared to a:
   - Vacuum cleaner full on
   - NetApp/EMC 4HU head (storage)
   - Old cisco or juniper cores
4. Maybe a 2nd system like that would fit in my room - but I thinks it is very impossible to have more
   than 2 or these systems in a room without climate control
5. The hashing speed of the 5970 started with ~250 mhash and decreased constant to 194mhash after like 10min - I am not sure
    for the cause - maybe I don't have enough power - don't know
6. if you are richy rich you can buy some custom water cooled extensions for the HD cards don't known like 500-600 EUR for both.

I did not plan this system for bitcoining but a dedicated opencl computation system... I am
working with cuda/cal/opencl sind 2-3 years mainly with crypto. I am trying to optimize BitcoinMiner.cl because in my opinion
you can have a big speed up by having kernel run times of 5-7 seconds each - of course this only works on a dedicated system
without needs for gfx refresh rates )

If you have questions please ask.

If you have tricks for increasing/optimizing the computation speed without overclocking please tell me

happy computing

(sorry for language difficulties not a native speaker)