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Overclocking with an AMD 8th Generation platform

WARNING: Overclocking will VOID your warranty and may damage your hardware and/or cause loss of data ! Everything you do is AT YOUR OWN RISK !!

The most important thing to keep in mind before your even consider to overclock is:
Know what you're doing and be aware of the possible consequences!

Overclocking means you're going to sacrifice your warranty and put your hardware and data at a certain risk in order to attain better performance.
Just how much risk you're going to take is entirely up to you, but if you fry something in the process, it's your problem – there'll be no RMA.

To get a basic feeling how overclocking works on an AMD 8th-Generation platform, we'll have a look at some examples:

I won't go into any details in regards to cooling, voltages, whatever – the purpose of this Article is merely to give you a basic architectural overview, so you'll be able to understand what's going on 'behind the scenes' when overclocking.

Our first example will be a 754-pin Athlon 64 3200+ on VIA K8T800-based motherboard:
With the base-clock running at its default 200MHz, all other clocks are running like they should – AGP is at 66MHz, PCI runs at 33MHz, the processor's core-clock runs at its default 2000MHz, the HT-link runs at 800MHz and lastly the DDR400 memory also gets its default 200MHz memory-clock.
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Clocking example: Athlon 64 3200+ (754-pin), K8T800 chipset


Now if we change the base-clock's frequency (either in BIOS/CMOS Setup or with Software), we can see how just about every other clock's frequency changes aswell.
AGP is running at 70MHz and PCI runs at 35MHz while the CPU core-clock gets overclocked to 2100MHz and the HT-Link is overclocked to 840MHz since we didn't change their respective multipliers. As a result of the higher CPU core-clock, the memory-clock is also overclocked to 210MHz.
We could change the CPU core-clock- and HT-multipliers as well as the memory-divider to get lower clocks, but the AGP- and PCI-clocks would still be overclocked.

For our second example, we'll use a newer motherboard based on the Nvidia Nforce4 chipset, which features independent PCI & PCI-Express clocks and our processor will be a 939-pin
Athlon 64 3700+. Initially, everything runs at default speeds – the CPU core-clock runs at its default 2200MHz, the HT-Link's clock runs at 1000MHz which is default for 939-pin parts.
PCI and PCI-E clocks are provided by a separate PLL, so we don't see them here in our example as they will remain 'locked' at their default speeds.

Again, we'll change the base-clock albeit a bit more radically this time as it'll be set to 250MHz.
Apart from the much higher CPU core-clock, both the HT-Link's clock and the memory-clock are overclocked way beyond their default speeds. Stability-issues are almost inevitable at this point, especially if we don't have some very good overclocking memory – if the system will even POST to begin with.
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Clocking example: Athlon 64 3700+ (939-pin), NForce4 chipset


We can maintain the high CPU core-clock while bringing down both the HT-Link and memory to more reasonable frequencies by changing a few things before raising the base-clock to 250MHz:

First, we'll lower the HT-Link's multiplier from its default x5.0 multiplier to x4.0 which will bring our HT-Link's frequency back down to its default 1000MHz – no more problems there.
Then, we'll change the memory-divider to a higher value, which is normally used when running slower PC2700 memory. At the processor's default clockspeed of 2200MHz, a /11 divider will make the memory run at 200MHz (for PC3200) whereas a /14 divider will make it run at 157MHz.
Normally, PC2700 memory has a default frequency of 166MHz, but since only integer dividers (= whole numbers) can be used, a /14 divider is as close as you'll get without going beyond the default 166MHz which would overclock PC2700 memory.
So we set the memory-divider to /14 – in most cases, this means setting the memory-clock to PC2700/DDR333 memory in BIOS/CMOS Setup as you won't be able to specify an actual (numerical) divider in most cases. The higher /14 divider brings our memory down to 196MHz, slightly below default, but definitely stable.