As we saw in the Intel Haswell i7-4770K & i5-4670K Review Haswell brings some new overclocking methods and challenges to the table. Overclockers have to find a balance between maximum CPU clocks, memory clocks, and uncore. You can no longer expect to easily max out CPU and memory clocks as you will likely have to sacrifice one or the other for any degree of stability.
Additionally, with the VRM on die, Haswell temperatures exceed even those we saw with Ivy Bridge, so stock Intel coolers no longer cut it when pushing frequencies. Many users are moving to high end water cooling setups to manage the heat produced by Haswell chips. In this section, we will bring you through the process of manually overclocking a retail 4770K on the Maximus VI Hero and hopefully you can learn a few tips and tricks to help with your own Haswell overclocking.
Before getting into manual overclocking results we did want to put a caveat on these results. We are using a high end water cooling system with a powerful pump and two double heatercores equipped with four 120mm fans to dissipate heat. Also, we are now using a RETAIL CPU.
Starting with the CPU overclock and leaving the RAM below spec and uncore at stock we started at the 4.6GHz achieved with 4-Way Optimization and slowly went up from there while keeping a close eye on temperatures.
Since voltages and temperatures were already high we weren’t sure how much further we could push the CPU overclock but we managed to make it to 4.7GHz at 1.365v (manual voltage) but at that point temperatures were starting to throttle a bit under AIDA64 load so we felt it would be safest to stop there.
When your load temperatures approach 90C it is safe to say that the chip is more than making out a given cooling solution. We were pleased however to be able to gain 100Mhz over 4-Way Optimization with less voltage than was set for 4.6GHz (1.365v vs. 1.400v).
With a stable overclock of 4.7Ghz, the next step was to focus on memory clocks. Our G.Skill Trident kit is rated for 2800Mhz so with a first attempt we tried for 2800Mhz on the RAM at stock timings of 12-14-14 2T. That was stable there so we tried for 2933Mhz which wasn't possible. The issue is the L3 cache which is tied at the hip to the memory controller frequency so when CPU clocks are maxed out, the CPU will be running out of headroom for I/O which can lead to a number of stability issues.
With 2933 a no go, we managed to stabilize 2800Mhz at 11-13-12 1T at 1.65v, which is a nice improvement over the 2400Mhz at 12-14-14 that we had with 4-Way Optimization!
The next step is to move up uncore until stability starts to wane. Uncore frequency clocks similar to the CPU frequency and it has its own voltage called CPU Cache Voltage. Ideally you want uncore to be 200-300Mhz below your CPU clocks and after some tweaking we managed to stabilize uncore at 4400Mhz. SuperPI and Cinebench are very handy for testing exactly which combination of CPU speed, memory speed, memory timings, and uncore frequency will yield the best results. Highest is not always best so take your time and run some benchmarks so you know you have the best overclock for your system.
After all was said and done, we found the optimal configuration for our setup was 4700Mhz (47 x 100) on the CPU, 2800Mhz on the memory tightened to 11-13-13 1T, and 4400Mhz on the uncore. For voltage we preferred the manual mode because you know exactly what you will get under load. With the VRM on die vdroop is basically non-existent so there is no need to compensate for that.
Here are a few tips to help with stability:
After finding that optimal point for our manual overclock, of course we wanted to play with our memory and see what kind of overclocks we could get on the new Haswell platform.
First we tried out the 2800Mhz 12-14-14 kit of Trident to see what kind of headroom it had left in it. Using an ES CPU in the Deluxe review we were able to push the Trident to 3000Mhz but our retail chip wasn’t quite as strong on the IMC front and the memory ended up at 2970Mhz.
Much to our surprise, we were actually able to push the four modules (totaling 16GB) further than either kit would clock independently. ASUS T-Topology for memory likely has something to do with that. In the end we got so close to the 3000Mhz holy grail but no matter the voltage or timings we could not complete a 32M at 3k. We ended up with a 16GB overclock of 2996Mhz at 12-14-12 2T which is quite impressive.
BCLK overclocking on the Haswell platform is linked to the CPU straps and you can typically scale 3 to 5 BCLK from the strap before running into stability issues. The straps available are 100, 125, 167, and 250; however it is pointless to even have the 250 strap in the UEFI because it is not useable. ASUS also added “secret sauce” to the flagship boards the Deluxe and the Maximus VI Extreme to run the 200 strap on some CPUs however the Hero doesn’t have it.
That said, the natural place to start was with the 167 strap. Problem was no matter what we tried, as soon as the BIOS settings saved the board would turn off and we would have to clear CMOS to recover. It is likely CPU related though, because the retail Haswell chips simply don’t overclock like the ES chips do. In the end our max BCLK was in the low 130s.
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