As some of you may know, I've been doing a bit of research into the effects of increasing DAG file size on hashrate. The reason behind it being the dramatic drop of hashrate on GTX750Ti on Windows as DAG file size increased. So far, I have concluded that other modern Nvidia cards are relatively safe until the DAG size hits 2GB, but I don't have any data on AMD cards yet.
Today, I've ported my CUDA dag simulator to OpenCL, but as I don't own any AMD cards, I still don't know what the results are. Attached is a (64-bit) Windows binary that can show you the approximate ethminer hashrate with a given DAG size. I would be very grateful if some of you could do some tests with me.
[big update to this post since a major update to the test program]
By default, the program will generate a pseudo DAG file with a size matching your GPU RAM (or a max of 4GB) and test bandwidth/hashrate with incremental steps from 128MB up until the maximum possible.
The results will be written to a tab-delimited csv file called results.csv.
Using a spreadsheet program like Excel, you can easily convert this to a graph like this one for my GTX780:
x-axis is DAG size in MB, y-axis is hashrate in MH/s. Because the test uses a simplified dagger loop without the SHA3/Keccak stages, you may see slightly better results than with the real ethminer.
If you have less system RAM than your GPU RAM, you can set the maximum using the 1st command line parameter:
This will test DAG size up until 2048MB (= 2GB)
I think most AMD cards will be fine, but you never know. If you have more than one GPU in your system, you can use the 2nd command line param to select a different card:
dagSimCL.exe 4096 1
will measure on the second card (1st card is 0). Because the command line switches are not very clever, you will have to set the first one to your GPU RAM or higher like shown here.
If you have problems with multiple openCL platforms installed, you may add a third cmd line arg to select the right platform:
dagSimCL.exe 4096 0 1
will measure on the first card on 2nd platform.
Source code and most recent binaries here: https://github.com/Genoil/dagSimCL
. Haven't tested on Linux. Also no Linux makefile available yet.
Most recent win-64 binaries also in the attached ZIP.
Please post results including results file attached. Thank you!