HTT is something specific to the K8 architecture (Athlon64, Opteron, etc) and not to nForce4. Since with this architecture, AMD moved the memory controller directly onto the CPU (instead of being on the motherboard), there needed to be a way to connect to the rest of the system. HTT also allows processors to directly connect with each other instead of taking long trips through the chipset on the motherboard. As bob661 said, a majority of HTT run at 800MHz or 1000MHz. If you think of HTT as your FSB from the good ol' days (a semi-dangerous notion, as there's no "true" FSB on the K8 architecture), then you can see where you get the 800MHz or 1000MHz, as 4x or 5x 200MHz (ie, DDR400 speed).
Because of the way that the processor requires the timings on the HTT, if you're looking at overclocking your memory (ie, to DDR500 speed) you'll need to change the HTT multiplier -- as a rough example, 4x250MHz = 1000MHz, so DDR500 memory requires a HTT of 4x to achieve the 1000MHz required by the processor. So yes, the HTT is very crucial to how you're looking at overclocking your K8 processor. This is a very rough guide, and if you're looking at overclocking seriously, the K8 architecture is a different beast than what has come before, and I'd recommend reading more in the forums here about it.
From a year and a half ago, Anand wrote a very indepth intro to the K8 architecture. Page 6 especially deals with the HTT, though the entire article is a very good read --
http://www.anandtech.com/cpuch...ts/showdoc.html?i=1815
I'd also take a look at the HTT FAQ over at hypertransport.org --
http://www.hypertransport.org/tech/tech_faqs.cfm
Hope this helps you (and others) out some!
Discussion Zen 5 Speculation (EPYC Turin and Strix Point/Granite Ridge - Ryzen 9000)
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