Also, I remembered that the cgminer.conf file has temp overheat and cutoff options. They may have something to do with your computer shutting down.
"temp-cutoff" : "90,90",
"temp-overheat" : "85,85",
"temp-target" : "75,75",
Are you suggesting I add this to the config file I listed above? ***edit*** I just re-edited my previous post - that is my bat file listed there. I am not running it with the config file. I am running it from the bat file.
If you'd rather add those settings to your batch file, append this to the end of your cgminer line:
--auto-fan --temp-cutoff 90 --temp-overheat 85 --temp-target 75
If you want to control the temperatures for the cards individually, you can use a comma-separated list as illustrated above (i.e. --temp-target 70,76).
As to your problems with the system shutting down, it certainly sounds like your power supply is the issue. The shutdown symptoms you describe are typical of a PSU's protection circuits shutting it down (this is a good thing actually... ultra-cheap PSUs usually don't have these protections and instead simply start on fire!). You mentioned your PSU is a Cooler Master GX-750. Typically, Cooler Master makes decent power supplies... but the GX-750 looks like it may be an exception. Check out this review:
http://www.jonnyguru.com/modules.php?name=NDReviews&op=Story&reid=188The unit was unable to continuously deliver the full 720W on the 12V rail that it's rated for. Because the PSU is so inefficient, its over-temperature protections would trigger before the unit could even reach its maximum output capability. This sounds quite like what may be occurring for you which would explain why it might seem to work sometimes and other times not so much. I would guess that the times where it successfully runs primecoin+litecoin for a short while it's not quite hot enough to trigger its over-temperature protection. After a few minutes of the load caused by primecoin+litecoin mining it finally heats up enough and trips the over-temp protection shutting the system down. Additionally, your system may be at the limits of your power supply's overcurrent protection which could be the cause of the immediate shutdowns when starting a miner. This is why you have to use the switch on the back of the power supply... to reset the protection circuit. This usually wouldn't be necessary if the problem were elsewhere (i.e. the electrical circuitry of the building, the motherboard, cpu, gpu, etc).
I suspect that there's a triad of things going wrong here that are coming together to cause your problem.
1.) What's the temperature of the room in which this mining rig is housed? Is it air-conditioned? A high ambient temperature may be contributing to this issue. Make sure that the cooling fan of the PSU is spinning up to 100%... sometimes PSUs have defective fan controllers.
2.) Are your 7970 cards overclocked? Are they undervolted at all? What about your CPU? The AMD FX-8350 can draw quite a bit of power and a lot of this power comes from the +12V rail just like for your GPUs. I would guess that you're already over 50A on the +12V rail and coming up on the 60A rating of your PSU, assuming it can even supply that much.
3.) As mentioned before, your PSU -- while adequately
rated -- may not actually be providing the output that you need to run your system. If your PSU is performing like the one in the review (
http://www.jonnyguru.com/modules.php?name=NDReviews&op=Story&reid=188), it's really only giving you about ~600-650W of real output at best which is inadequate for your system (when mining primecoin+litecoin simultaneously). Add to this the fact that a power supply's output tends to degrade with age (how old is yours?) and we really start to run into issues. That said, even if your PSU is/was capable of delivering the power that your system needs, you're still running up against the red line of it's capabilities which is never a good thing.
I don't believe that the issue lies with your CPU, motherboard, or the electrical circuit to which your system is connected. Your power supply seems to be the culprit but this is just my opinion based on the information provided. The other 650W PSU that you tried testing with probably had the same problem as your 750W. It's not necessarily a bad PSU, just inadequate. Without significant undervolting, 650W (~54A or less on the +12V rail) is really pushing it for two 7970s + a monster CPU at 100%.
I always hate to suggest for someone to run out and spend money on new equipment so here's what I'd try for a solution: If possible, undervolt/downclock your 7970s a bit. I run mine at just 902Mhz core and 998Mhz memory at 980mV and still obtain 640Kh/s each. At these clocks and voltages, each card only uses ~170W-180W -- super efficient. If your cards are factory volted at 1.2V core and 1.6V memory like some... they can use almost 280W a piece with a mild overclock. Knowing this, it's easy to see how you can easily exceed the capabilities of some power supplies.
If you manage to get your cards undervolted/clocked and find that the system can then run stable while mining primecoin+litecoin, I'd look into buying a beefier, higher quality PSU. I would suggest a Corsair, XFX or Seasonic 850W unit with a silver or better efficiency rating (they can be pricey, but worth it). You probably won't need to throw away your current PSU, either; just save it for a less demanding non-mining system.
