Minimum CPU requirements for dual 5870

[mores]

I have been mining a single 5870, and now I have decided to go dual 5870s.

I have a certified crossfire 750 watt power supply
Motherboard with 2 PCI Express x16 slots

I expected to get 2x the performance 325 Mhash/s x 2 = 750 Mhash/s ( aprox )

But it turns out my rate was only 425 Mhash/s. Load was running around 5, so I am assuming my CPU is too slow to push both cards to the expected rate of 750 Mhash/s.

What is the minimum cpu required to get 750 Mhash/s from dual 5870 using crossfire ?

[pekv2]

I have been mining a single 5870, and now I have decided to go dual 5870s.

I have a certified crossfire 750 watt power supply
Motherboard with 2 PCI Express x16 slots

I expected to get 2x the performance 325 Mhash/s x 2 = 750 Mhash/s ( aprox )

But it turns out my rate was only 425 Mhash/s. Load was running around 5, so I am assuming my CPU is too slow to push both cards to the expected rate of 750 Mhash/s.

What is the minimum cpu required to get 750 Mhash/s from dual 5870 using crossfire ?

First off, which processor do you have? make/model.

[John (John K.)]

I have been mining a single 5870, and now I have decided to go dual 5870s.

I have a certified crossfire 750 watt power supply
Motherboard with 2 PCI Express x16 slots

I expected to get 2x the performance 325 Mhash/s x 2 = 750 Mhash/s ( aprox )

But it turns out my rate was only 425 Mhash/s. Load was running around 5, so I am assuming my CPU is too slow to push both cards to the expected rate of 750 Mhash/s.

What is the minimum cpu required to get 750 Mhash/s from dual 5870 using crossfire ?

What's your miner? CGminer or GUIMiner? The CPU is kind of out the equation here, as I've successfully run 5970's with a paltry AMD Sempron single core.

[phantitox]

i was using one FSP 800W Gold when i have my old 5870 then i add another 5870, have to switch my power supply, i think you should beware of the supply before the cpu, also the most cpu hunger i see is the phoenix miner, powerful miner for the gpu, but over Aggression 10 i takes 15% cpu for each instance :-/

[mores]

I currently have an Intel Pentium 4 3.20GHz

I am running CGMiner

[mores]

Here is some additional info from my setup.

$ ./cgminer --ndevs
 [2012-07-10 13:05:46] CL Platform 0 vendor: Advanced Micro Devices, Inc.
 [2012-07-10 13:05:46] CL Platform 0 name: AMD Accelerated Parallel Processing
 [2012-07-10 13:05:46] CL Platform 0 version: OpenCL 1.2 AMD-APP (923.1)
 [2012-07-10 13:05:46] Platform 0 devices: 2
 [2012-07-10 13:05:46]    0   Cypress
 [2012-07-10 13:05:46]    1   Cypress
 [2012-07-10 13:05:46] Failed to ADL_Adapter_ID_Get. Error -10
 [2012-07-10 13:05:46] Failed to ADL_Adapter_ID_Get. Error -10
 [2012-07-10 13:05:46] ADL found less devices than opencl!
 [2012-07-10 13:05:46] There is possibly more than one display attached to a GPU
 [2012-07-10 13:05:46] Use the gpu map feature to reliably map OpenCL to ADL
 [2012-07-10 13:05:46] WARNING: Number of OpenCL and ADL devices did not match!
 [2012-07-10 13:05:46] Hardware monitoring may NOT match up with devices!
 [2012-07-10 13:05:46] GPU 0 ATI Radeon HD 5800 Series hardware monitoring enabled
 [2012-07-10 13:05:46] 2 GPU devices max detected$

I also found this https://bitcointalk.org/index.php?topic=10103.0 like an entry in this post my setup also saw kworker was eating up my cpu.

[phantitox]

try phoenix or another, and star with lower aggression the workers get max use of the cpu in one minute, after that you should see the max use of any worker, start with lower aggression and scale up

[davidj411]

We're using the cheapest Celeron 2.4ghz you can get on ebay and it works fine.

[mores]

I have seen threads reguarding:  export the var "GPU_USE_SYNC_OBJECTS=1" to CGminer to fix the "100% CPU usage BUG".

And use Ubuntu 11.04 64bit installed (NOT 11.10 or newer!!!) <- because there are crossfire bugs.

Is there any truth to these items ?

[mores]

Kworker is what controls the ACPI wakeup signals from the BIOS.

The latest kernel, well all of them since 2.6.35 have had issues with too many wakeups.

More info about problems with newer kernels....does anyone know of a submitted bug report so we will know when this issue gets fixed ?