Ok. After spending two hours typing this up last night and then having the misfortune of hitting the wrong button and losing it all......... I will try this again.
After Eight or so hours of trial and error I learned a few things in this endeavor.
First off I was very surprised to learn how precise your voltage needs to be at a given core clock rate. I was unaware that too much voltage would decrease your output just as too little would. Once I figured this out things went quick and smooth.
Secondly, I was just as surprised to find that faster memory is not always better. I was able to clock the memory all the way to 1450mhz stable. But I actually got better results at a lower rate.
For anyone new to overclocking don't forget these two points. It will save you a ton of time later.
So, what I ended up doing was selecting a core voltage that I felt comfortable with. It turns out that the 1300mv that I mentioned in my earlier post is in fact the highest MSI Afterburner will allow you to go. Now I am just looking to milk a few more FPS out of my system not create really expensive paperweights. The stock voltage on my cards is 1219mv. I decided to go with 1238mv. It's a nice tweak but I think it's not very aggressive. Afterburner allows for increases of just over 6mv steps. If it doesn't like the number you punch in it adjusts them for you.
I went for a round number of 1240mv but got knocked back so I just rolled with it.
Next I began running MSI Kombuster. I used the Kmark open GL4 and PhysX Benchmark at 1920 x 1080. ( probably not the best choice but it did the job) At each run I increased the core clock by 25mhz until the gain turned into a loss. I then backed down to the prior clock setting and began increasing it by 5mhz. When I hit a loss I backed down to the prior setting and reran the program to confirm the number.
Clocking the memory speed was performed the same way. It worked out well for me.
After I completed my initial tests I decided to go back and rerun them. I ran three runs at AMD's reference clock, three at the cards stock o/c, and three at my overclock.
When this was completed I then ran three runs at each setting using Heaven. I have to say I love heaven. What a great benchmarking tool. If you haven't used it try it out. It never seems to get boring watching it either.
So here we go.
System specs,
i5 2500k o/c to 4.0ghz
MSI Z77A G45 Gaming mobo
16GB Corsair Xms3 DDR3 @ 1600mhz
120GB Kingston SSD
2TB Seagate Baracuda
2 X MSI R7870-2GD5T/OC
Benchmark tool: MSI Kombustor
Kmark Open GL4 and PhysX Preset at 1920 x 1080
Reference clock
core voltage: 1219mv
power limit: +/_0
core clock: 1000mhz
mem clock: 1200mhz
Score: X1991 @ 66 FPS
Stock o/c
core voltage: 1219mv
power limit: +/_0
core clock: 1050mhz
mem clock: 1200mhz
Score: X2009 @ 68 FPS
My o/c
core voltage: 1238mv
power limit: +20%
core clock: 1180mhz
mem clock: 1350mhz
Score: X2055 @ 75FPS
Benchmark Tool: Heaven
1920 x 1080 With 8xAA
Preset: custom
Quality: Ultra
Tessellation: Extreme
Reference clock
core voltage: 1219mv
power limit: +/_0
core clock: 1000mhz
mem clock: 1200mhz
Results: Avg. FPS: 49.8
Score: 1256
Min FPS: 18.6
Max FPS: 114.5
Stock o/c
core voltage: 1219mv
power limit: +/_0
core clock: 1050mhz
mem clock: 1200mhz
Results: Avg. FPS: 51.0
Score: 1284
Min FPS: 18.8
Max FPS: 117.0
My o/c
core voltage: 1238mv
power limit: +20%
core clock: 1180mhz
mem clock: 1350mhz
Results: Avg. FPS: 56.2
Score: 1471
Min FPS: 19.6
Max FPS: 130.4
Conclusions:
I am sure these cards will o/c more than I have gone. I did actually go a little higher at one point but was concerned. At this obtained overclock I do not receive a large increase in heat. My case has six fans. I now run about 69 deg as opposed to 64 deg under sustained load with the card fans locked at 45% I can live with that. When I ran higher the heat raised ALOT. I hit 79 deg with the card fans at 90% at one point. ( At a much higher voltage). Glad I was watching closely.
Real world gains???? Actually yes. The real gain here is in smoothness. I don't see a big frame rate increase in the real world. But the min frame rate is higher in game. It was never unplayable by any means but it just seems to make things more stable and somehow more clear.
If anyone has any comments or suggestions to what I have done please feel free to post them. I am always interested.