Intel Core i5 661 Dual Core LGA 1156 Processor Review


Test Rig:
Intel Core i5 661
Asus P7PH55D-M EVO Intel H55 mATX motherboard
OCZ Platinum DDR3-1333 7-7-7 4GB Kit
OCZ Z Series 650 Watt power supply
Titan Skalli CPU cooler
Ikonik Zaria midtower
Windows Vista Ultimate 64-bit

The contact pins on the LGA 1156 CPU socket are very fragile, so be very careful not to touch them. Observe the “keys” on the CPU and CPU socket to determine the orientation of the CPU. Place the CPU into the socket, lower the retainer and place the edge beneath the locking lug located on the motherboard. Lower the locking lever and lock it in place.

Prep the CPU with isopropyl alcohol and a lint free cloth. Apply thermal compound to the CPU surface per manufacturer’s instructions. Be aware if you are using a CPU cooler with exposed heatpipes you will need to physically spread the compound on the CPU. Install the CPU cooler. Install the memory, you will use the second slot from the CPU and the last slot nearest the forward edge of the motherboard, the opposite from LGA 775 motherboards. If you are using four memory modules, install just two of them in the aforementioned slots, install the other two later after setting up the rig.

Intel Core i5 661 Dual Core LGA 1156 Processor Intel Core i5 661 Dual Core LGA 1156 Processor

Install the motherboard into the case and finish building the rig.

Intel Core i5 661 Dual Core LGA 1156 Processor Intel Core i5 661 Dual Core LGA 1156 Processor

The Core i5 661 operates at a stock clock of 3.3gHz, higher than the other processors in the series. The numbering scheme of the series isn’t exactly self explanatory, so I’m not going to try to guess. The 661 also lacks two features found on the other processors, Intel® Virtualization Technology for Directed I/O (VT-d), and Intel® Trusted Execution Technology.

Of course how easy or hard a processor is to overclock is mostly determined by the BIOS of the particular motherboard you are using. Intel’s LGA 1156 processors are particularly easy to overclock due to the lack of mandatory tweaks as were present in the LGA 1366 processors. Generally all that is needed is the Base Clock (usually known as BCLK) which is the same number we’ve always changed to overclock, changing the multiplier if you feel the need, and increasing the CPU voltage.

Make sure that the GPU frequency isn’t sync’d with the CPU freq. This board does it by default and I had to disable it. That is a tweak for another day. I always disable Intel SpeedStep and idle modes while overclocking.

Some motherboards allow for CPU overclocking independent of the memory, this particular board increased the memory along with the CPU clock. If you are using DDR3-1333 memory or less you should make sure the memory speed doesn’t get too high, I tend to keep it much lower than the max to ensure a failed overclock isn’t due to the memory speed. MAKE SURE YOU DO NOT SET THE MEMORY VOLTAGE OVER 1.65V! As all other LGA 1156 and LGA 1366 processors, you will damage the CPU’s internal memory controller. These processors are to be used with Low Voltage memory.

The i5 661 easily overclocked to 4.0gHz. I decided to stop at 4.28gHz, which is a 28.5% overclock. Undoubtedly it will go higher, but I always like to get comfortable with a processor before trying for a max overclock. I don’t expect most owners of this processor will be overclocking it anyway. I was pretty amazed, it did this overclock at 1.28v with no issues whatsoever.

Intel Core i5 661 Dual Core LGA 1156 Processor Intel Core i5 661 Dual Core LGA 1156 Processor

I haven’t been able to find anything on Intel’s site, but supposedly the max CPU temperature with the i5 661 is 72C. The shutdown temperature of the LGA 1156 i7s is 90C, I would expect the dual core i5s to be less, so I’m not surprised. Though this processor seems not to be a hot running CPU, the ambient temperature of the room was particularly cold, around 60F (long story) so I really couldn’t tell what kind of OC temps to expect. A friend was reviewing the same processor at the same time and he said that he never saw 72C with the stock cooler running a 4.0gHz overclock at normal room temperature.