HT Link frequency:
Before we start analyzing the obtained results, let's find out what the HT Link is designed for.
In Intel-terms, the HT Link frequency is quite similar to the FSB: taking care of the communication between processor and Northbridge, which features for instance the PCIe lanes, sata ports and audio support. The faster the link between processor and Northbridge, the more data can be transferred between both and, in theory, the higher the performance will be. Without going to much into detail, it's necessary to know that the current HyperTransport link is clocked at a frequency of 1800MHz, which is 1000MHz higher than the first edition of the HT link used on the s754/s939 Athlon64 platforms. Note that although the original HT Link frequency was set at 800MHz later revisions of the s939 motherboards had a stock HT Link frequency of 1GHz.
Test settings:Core frequency: 3000MHz
HT frequency: 200MHz
Northbridge frequency: 1800MHz
Memory frequency: 400MHz (1:2 divider)
Memory timings: 4-4-4-10 2T Ganged
HT Link frequency (200 - 1800MHz*)
(Click for bigger version)
The HT Link frequency is not what what we'd call interesting in terms of overclocking for performance. The difference in performance between very low and high frequencies is in most benchmarks non-existing, although we see a noticeable performance increase in the 3D benchmark. Note that the effect of overclocking the HT link frequency depends on what type of video card you're using. IGP's and high-end video cards (for instance dual gpu cards) will benefit more from HT Link overclocking, because they rely on high pci-e transfer rates. Low- and middle-end cards, which are less powerful and have a lower transfer rate, will benefit a lot less.
*: Because of the NB frequency of 1.8GHz, we were not able to test HT link performance scaling beyond 1.8GHz. The HT Link has to be equal or lower than the NB frequency at all times due to the design.