Radeon R9 280X Litecoin mining and Sweet Spot for 700KHash/sec (part 1)
With the scarcity of the excellent Radeon 7950 for mining Litecoin, the focus has been shifted to some other good alternative graphics cards. Radeon R9 280X, which is essentially a rebranded 7970 is another good option for GPU mining. I have managed to get my hands on a few Gigabyte R9 280X, MSI R9 280X and PowerColor R9 280X.
You can check out the tutorial on How to build your own Litecoin mining rig with Radeon R9 280X if you are interested.
After some tweaking, I have managed to get the Gigabyte R9 280X to produce around 700KHash/sec per card. Let us look at how to configure the Gigabyte R9 280X for higher hashrate and possibly lower power consumption.
How to optimize Gigabyte R9 280X for Litecoin mining
Since the 280X is a rebranded 7970, it is possible to undervolt the cards using the VBE7 method that i have outlined in the previous tutorial: How to modify video BIOS to undervolt GPU in Linux. My Gigabyte cards run completely stable at 1094mV, so if you are using my undervolting method, simply replace the 1081mV that i have recommended for 7950 with 1094mV.
18/12 Update: Further tweaking shows that the card is stable at 1075 mV.
These are early test results and i expect it to go even higher with some tweaking. But this should give you a good start with acceptable hashrate for the time being.
For this test, i am using BAMT version 1.1 with the latest AMD Catalyst drivers installed and CGMiner 3.7.2. You may learn more about setting up BAMT in my tutorial: Litecoin BAMT version 1.1 – Easy USB Linux mining distro.
I get the best result from this CGMiner configuration:
-g 2 -w 256 -I 13 --lookup-gap 2 --thread-concurrency 8192 --gpu-engine 1020 --gpu-memclock 1500
This configuration gets me around 700KHash/sec on each card with a low reject ratio. I have read about others obtaining hashrate as high as 750KHash/sec on other brands and configurations, but with my limited testing, this is the result that i got without compromising stability.
For other brands of R9 280X, you can try 1060MHz or 1080MHz for the core clock speed as a lot of people are getting good hashrates with that setting.
I will try to get the configurations for the MSI and PowerColor cards for you all after i am happy with the output from Gigabyte.
20/12 Update: As promised, here is part 2 of the tutorial on MSI and PowerColor cards: Radeon R9 280X Litecoin mining and Sweet Spot for 700KHash/sec (part 2)
31/12 Update: Here is my updated CGMiner configuration for Gigabyte card: Litecoin Mining – Gigabyte Radeon R9 280X Sweet Spot for 730KHash/sec