Intel Haswell i7-4770K IPC and Overclocking Review

Intel's clock keeps ticking and today lands on a "tock" in the development cycle. The new desktop Haswell processor represents a new microarchitecture built on the tried and true 22nm process technology that we have come to know and love with Intel's current Ivy Bridge microarchitecture. But what does Haswell mean for the computer enthusiast?


Luck of the Draw?

From all the feedback that I am getting through motherboard makers about Haswell overclocking, the basic thread at this time in terms of getting "high overclocks" seems to be, "You need to have a good CPU." ASUS has tested a couple hundred Haswell processors at this time and this is ASUS’ specific feedback from that overclock testing.

  • 70% of CPUs can clock to 4.5GHz

  • 30% of CPUs can clock to 4.6GHz

  • 20% of CPUs can clock to 4.7GHz

  • 10% of CPUs can to 4.8GHz

    Overall you will find most CPUs capable of reaching 44x to 45x with varying levels of voltage.

These ASUS results were obtained with sealed water cooling systems that are comparable to a Corsair H80/H100 configuration or extremely efficient air cooling with 120mm push/pull fans while applying a maximum core voltage of 1.275v under full thread load conditions.

Obviously it is very early in terms of Haswell retail processor production, and we are still not sure what we will see in terms of i7-4770K retail purchased Haswell overclocking headroom. We will be buying a couple of Core i7-4770K processors this weekend and see what comes out of that. Going on the above information, it would seem that getting a 4.8GHz-worthy Haswell sample will be about a one in ten shot with "normal" sealed water cooling systems.

Overclocking the Haswell i7-4770K processor that was sampled to HardOCP directly from Intel was extremely simple using two ASUS Z87 series motherboards and we will describe on that on the following pages. From the information above we can assume that we got a "golden" sample directly from Intel, or were extremely lucky when it came to the luck of the draw.

All about the Cooling

As most of you reading this have already guessed, overclocking Haswell is going to be very dependent on your cooling system. Many of you that have put off water cooling in the past are very likely to be about to take the plunge. If you are going to stick with air cooling, you will likely need a very efficient system. ASUS went as far as to make cooler recommendations based on its overclock testing, which at this time I have to consider it the most informed opinion. Given the wide variety of voltages ASUS has seen at various clock speeds, it made some recommendations based on CPU core voltage needs.

For voltages up to 1.250-1.265 a Cooling solution meeting a minimum of a Corsair H80i is advised, superior performance can be offered by moving to the H90 or higher performing dual fan closed loop solutions.

For voltages up to 1.275-1.300 a cooling solution meeting a minimum of a Corsair H100i is advised.

For voltages up to or greater than 1.300v a high performance water cooling system is recommended. Minimum recommendation would be a unit such as Koolance EX2-755.

For voltages up to or greater than 1.350 a high performance water cooling system is recommended. Minimum recommendation would be a unit such as a Koolance EX2-1055.

Keep in mind these recommendations are based on controlling peak temperatures and loads under synthetic stress applications. For nominal real world usage load temperatures will be considerably under that of stress tests.

The last paragraph above is very interesting about synthetic stress applications and I will be addressing this more on the next page.

To put it in a nutshell, ASUS’ experience was that any core voltage over 1.2v accompanied by heavy workloads puts the enthusiast into water cooling territory and ASUS has experienced certain 4770K sample CPUs that have required 1.2v vCore just to hit 4.3GHz. From what we have seen, "high end" overclocking will require a good water cooling system. Surely there will be some exceptions to the rule, but I would not expect to be part of that crowd.

Memory Speeds

We are finding that hitting some tremendous memory speeds have been fairly easy with our sample 4770K. We have 8GB sticks of Corsair Vengeance DDR3 that are rated at 2400MHz (10-12-12-31) and we have found that hitting 2400MHz is not a chore, but there is a caveat, and it comes back to your specific processor. The likelihood of running 2400MHz RAM clocks decreases as your CPU clock speeds increase. Your specific processor may be capable of doing 4.8GHz, but only with a memory clock speed of 1600MHz, or luck of the draw might allow you to do 2400MHz with a 4.8GHz CPU clock. On the other hand, your Haswell may only be stable with a 4.5GHz processor clock and work just fine with 2400MHz memory. Again, a lot of this is going to come back to cooling. Given the huge bandwidth that we already enjoy with DDR3 at 1600MHz, this should likely be of little concern to most of us unless you are simply looking to post that uber-score with your favorite benchmark.

Worth noting here is that memory training does occur during POST. This is what ASUS had to say:

This is an important aspect to keep in mind as it can "destabilize a thought to be stable overclock." ASUS has incorporated advanced control parameters to help maintain memory training parameters that have yielded stable results.

I did not have any issues with this at all, but ASUS specifically noted this may happen with mixed DIMMs and at higher frequencies. One way to possibly get around this new MRC training standing in your way is to disable the Fast Boot options in the BIOS. Doing so will allow more time for the MRC to do a more complete training on the modules you have installed.

The Strap is Back

Intel has included a new "Gear Ratio" better known to all of us as CPU Strap adjustments. The Straps are 100, 125, 167, and 250. What the strap adjustment does is allow you to run a higher-than-100MHz BCLK on the processor without impacting the PCIE/DMI controllers by delinking the CPU from the attached busses. My particular CPU would run at 125 Strap, but had issues with 167. I have not had a lot of time to spend playing with this "new" feature, but surely there will be value to some of you as is it quite possible that using the CPU strap will allow you to eek out some overclocking headroom as well as performance. The use of Strap will also impact your memory frequencies so the addition of Strap does give you some flexibility there as well when it comes to choosing or tuning your memory speed.