Intel Core i5 661, Core i5 750 and Intel H55TC review - Tech cont'd
Author: Vedran Dakic
Date: 10 Jan 2010

It has two physical cores and 4 MB of L3 cache, which effectively makes it half of Lynnfield. The other part of the LGA 1156 package contains the GPU, PCIe and memory controllers, and is connected to the CPU with a QPI (Quick Path Interconnect) link. The second die is made in the ‘old’ 45 nm production process. So, in fact, Intel has just moved the Northbridge to the LGA 1156 packaging.

The two cores of the i5 661 processor support HyperThreading, which, with the increased CPU clock over 3 GHz, should make them pretty competitive against the old quad core LGA775 CPUs.

The main difference from Lynnfield CPUs is the removal of the memory controller from the CPU to the ‘GPU’ part (or a return to the chipset if you like). Combined with the lack of support for DDR3-1600, the memory system should take a hit. How big, we will see later.

Parallel to the introduction of i5 Clarkdale CPUs, Intel introduced i3 versions (no Turbo Boost) and Pentium versions (no Turbo Boost, no HyperThreading and 3 MB of L3 cache). These processors are also differentiated by the GPU clock. The one we have before us today operates their GPU at 900 MHz, and is the only one to get that clock. Other i5 and i3 variants have a clock of 733 MHz, and the Pentium branded one has a 533 MHz CPU clock.

As we have seen with previous Lynnfield CPUs, depending on the load, CPUs could be overclocked up to 3.60 GHz, which was over 600 MHz. Now, the cap is even further at 3.73 GHz, but the nominal frequency is higher as well, so the increase itself is about 300 MHz. That only applies to i5 series of CPUs, as the lower versions do not have Turbo Boost enabled.