Unstable and too hot at 4.5 or 4.6ghz

[Padlorr]

Hi folks, I could use some input on my OC attempts. I'm having trouble getting a stable OC beyond 4.4ghz.

My machine is as follows:
- Asus Crosshair V Formula
- AMD FX-8150
- Corsair H80i watercooling system (w/ the DC fans)
- 2x Powercolor 2GB Radeon HD 7850's in Crossfire
- 16 GB G Skill DDR3 (F3-14900CL10-8GBXL)

My goals are to get the CPU to 4.5 or 4.6ghz using the cpu multiplier, and get the HT and NB both at 2600. At 4.4ghz I'm setting 1.4v, but I can't seem to find the right volts at 4.5 or 4.6 to keep it stable and at reasonable temps. When I set volts high as 1.45 or above my cpu temps go over 75 C and the core temps get as high as 62 or 63 C, often shutting the system down automatically. Does those kind of temps seem high with my cooling set up (H80i in push/pull config to draw air into the case)? I've tried various methods of applying thermal grease from spreading to the dot method.

I'm trying not to overclock the HTT, so leaving that at 200, because my RAM won't boot above 1866mhz but I'd like to keep it at least at 1866. I've set both the HT and NB to 2600, and I've left all voltages on Auto. When I try to set the CPU/NB voltage to anything other than Auto I get errors in prime95 or AMD Overdrive stability tests. I've also noticed that while the system is stable in those tests with HT at 2600, it is actually flaky and I get random and erratic UI issues (e.g. windows open or close erratically). I've tried increasing the HT volts to 1.25 and NB volts to 1.15 but it's more stable on Auto (1.20 and 1.10 respectively).

Thoughts on any of the above are welcome!

Thanks!

[HiVizMan]

It could just be that your CPU can not do more than that with the cooling you currently have. I find that a bit surprising I must say.

You can manage your memory using the different dividers as you know, so changing the HTT above 200 should not be an issue. 215 or 220 are normally quite the sweet spot and your ram will have head room too.

Might be worth exploring those option.

Look at the voltages that are being set while on auto and write them down some place. It could be one or two are a touch too high and may be the cause of the heat production.

[Padlorr]

Thanks, I'll play with the HTT between 215 and 220, and I'll make a note of the voltages on Auto. The main one would be CPU/NB and it's typically getting higher than the Vcore on auto (currently 1.488 v at idle). As I mentioned above, I've been unable to get it stable without setting it to Auto but this should probably be my next area to focus on. I have suspected that's driving the heat up a good deal.

[HiVizMan]

Will check back here later to see how you are getting on. Just keep an eye on temps please.

[Padlorr]

Ok, I burned out a 4 pin connector to the motherboard, which I noticed when I smelled burning plastic and pulled all the power connectors. I didn't realize there was an 8 pin connector option, so I'm guessing my overclocking (cpu, nb + HT) was just too much for that 4 pin connector. My question is, should I have both an 8 pin and a 4 pin connector plugged in? Is there any benefit (or harm) of connecting both? The manual suggests you should just connect one or the other.

Also, the manual hints that you should connect a 12v molex power connector to the EZ_PLUG to support multiple graphics cards. I have 2 Radeon 7850's each with their own power connector, so should I also connect another 12v cable to the EZ_PLUG to supplement, or is that just for multiple cards that don't have their own direct power lines?

Finally, I had relied on Newegg's nifty PSU calculator to determine my 750W PSU was enough, but the Asus PSU calculator recommended 850+ for my rig. If 750W isn't quite enough, how would I know? Will the system just shut down when the PSU becomes overloaded? I have had unexplained shutdowns during Prime95 when running 4.5-4.6ghz overclocks, and the system seemed stable otherwise. Any thoughts?

Parker

[HiVizMan]

First question - yes indeed, if you have the connectors then populate the board with them.

Second question - with those two cards it would not be an issue, however if you have the spare connector use it.

Last question - PSU is not an easy choice. I work on optimal size being that wich will run my system at max load and only use 65% of the capacity. So if I have a 1000W PSU and I am running my system max out - them my load must only be 650Watts. A smaller PSU will do the job, but for how long.