Mining Litecoin on the Radeon 7970: The quest for 700kh/s

Here I am again with another post, wow.   This time I want to talk about Litecoin.  I’m sure most of you have heard of Bitcoin,  Litecoin is similar to Bitcoin and is just another form of Digital Currency.  I’m writing this with the assumption that you are familiar with “mining” and that you are here because you have a 7970 you are trying to mine with.  I’ve spent some time trying to get a decent hash rate out of the PowerColor HD7970 V3 I bought a couple of weeks ago and have laid out how I was able to get 700kh/s+ out of it below.

First let me say I would not recommend buying this card to mine with.  It’s stock cooling solution  is weak and you will never get the ram clocked high enough without a decent cooler.  You are better off going with a card that comes with a good stock cooling design.  I put an Arctic Xtreme 7970 on my PowerColor v3 and it seems to be doing a fairly decent job; my only real complaint would be that the cooler extends the length of the card so it’s likely going to be a hassle to install in a case that’s cramped.

After getting the cooler attached I started my quest to find a “Ghz” edition bios that would work.  Again, this is not a reference card so not every bios is going to work and I was unable to find anything pointing me in the right direction.  So with a little detective work, I was able to figure out that the Club 3D Royal Queen 7970 is based on the same board (LF R19FD) and it’s Ghz edition bios seems to work just fine on the PowerColor HD7970 V3.  You can find it at the techPowerUp GPU Database.  The Ghz edition bios seems to help achieve the 700+ kh/s rate these 7970 cards are known for.

I flashed the Ghz edition bios and set on my quest to unlock the mystery of the core/mem ratio.  The stock ratio is probably _not_ going to get you anywhere near the 700kh/s mark.   I spent some time going over forum posts and the SCRYPT-README for cgminer where the author of this great piece of Open Source software gives tons of solid advice about overclocking / tuning a 7970 for scrypt mining.  Building upon that I set out to find the highest  hash rate I could on my setup  by maxing out my memory frequency and adjusting the core clock until I found a rate that was getting me close to what I wanted to see.

Adjusting the core clock -/+ 1 mhz from the base ratio of .57 – 6 suggested in the SCRYPT-README I found that the optimal  ratio for my core clock and memory clock was “0.60835820895″.  Multiplying that by the memory frequency of 1775 suggests a core of 1080 and with that I get ~700kh/s using cgminer –lookup-gap 2 -I 13 –thread-concurrency 8192 -g 2.

Changing the core clock in increments of 1 up and down a few values from that  is worthwhile as I have observed all it seems to take is 1mhz to shed hashes from your rate.  Use the “magic number” as a guide and work from there and hopefully you see some similar results.   I’m using the 13.4 Catalyst drivers and MSI Afterburner to control my clocks but would expect the same results regardless of what method you use for that.  Your Catalyst version will most likely play a factor.

As with anything, your mileage may vary.  Driving a display and mining on the same card is going to affect your hash rate.  Other tasks that utilize your CPU will affect your hash rate and you may find better results if you use core pinning/processor affinity with your mining app.

So the end result of my quest resulted in my being able to get 700kh+ out of a 7970.  If anybody actually reads this and gives that magic number a shot, let me know how it works. :)