The Hypertransport or HT Link is the bus that the processor and memory use to communicate with the rest of the system peripherals, such as the video card, hard drives and USB devices. The AMD K8 processors used a first generation Hypertransport 1.0 specification, with either an 800 or 1000 Mhz speed, 1600 or 2000 Mhz effective. The K10 takes advantage of Hypertransport 3.0 which allows for up to 2600 Mhz or 5200 Mhz effective transfer rate, quite an increase over the HT 1.0 bandwidth!

Hypertransport = Bus Speed X Multiplier

Just as with CPU and Northbridge speeds, the HT Link is affected by the reference Bus Speed. In previous K8 implementations, the HT Multiplier or HTT had options of 1x through 5x. Motherboards with a HT 1.0 chipset tended not to be stable when overclocking much above 1000 Mhz, so it was important to reduce the multiplier when increasing the Bus Speed. Now with K10, settings up to 13x or higher are possible.


Depending on your particular BIOS, the HT Multiplier may be referred to differently. In the above example, it is called the SB (Southbridge) to K8 (CPU) Frequency, and carries a value expressed in Mhz. Just as the NB FID, the HT frequency setting is not a fixed value, but represents a multiplier that is used in conjunction with the Bus Speed to calculate the true bandwidth. There may also be a link width, such as 16 up, 16 down, indicating the 32 bit word size of the link.

In no case should the HT Link frequency be set higher than the NB frequency; this causes the system not to POST. It should always be equal to or less than the NB, for example with the Phenom 9850 the default NB is 2000 Mhz and the HT is also 2000 Mhz. In the BIOS above, options for the HT frequency setting are limited by the current selection for the NB in order to prevent this from occurring. Other BIOS may limit the value differently, or it might leave it up to the user to determine correctly. Therefore it is important to be aware of this limitation.

Now let's examine the memory settings.