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Overclocking

We decided to devote a separate part of our roundup to testing the mainboards overclocking potential. It turned out that the mainboards differ a lot here. These differences can be explained by the mainboards BIOS individual peculiarities as well as by the features of the chipsets they are built on. However, first of all I would like to dwell on the techniques used for proper AMD Athlon 64 3200+ overclocking, as this is the only Socket754 CPU available in the market today.

Athlon 64 processor frequency, like that of other processors from AMD is set as a [clock multiplier] x [processor bus frequency]. The nominal processor bus frequency of Athlon 64 3200+ is 200MHz, and the clock frequency multiplier is 10x. However, you should keep in mind that the processor bus frequency is  formal parameter for Athlon 64 systems. In fact, it is just a signal frequency which is used as a basis for CPU and other system components clocking. The Athlon 64 processor and the chipset are connected with one another via a special bi-directional HyperTransport bus, which is 8bit or 16bit wide in each direction and works at 600MHz or 800MHz (3x or 4x CPU bus frequency, to be more exact) depending on the chipset. As for the memory working frequency, it depends on the processor frequency, because as you know the corresponding memory controller is built into the Athlon 64 CPU. The actual working frequency of the AMD Athlon 64 3200+ processor is 2GHz, so the memory is clocked as 1/5, 1/6, 2/15 or 1/10 of the CPU frequency depending on the BIOS Setup settings, namely DDR400, DDR333, DDR266 or DDR200. as for the AGP/PCI bus frequencies, their clocking depends on the chipset. NVIDIA nForce3 150 clocks AGP/PCI asynchronously and independent of the processor bus frequency. VIA K8T800 sends to AGP 1/3 of the processor bus frequency. Moreover, VIA K8T800 theoretically allows setting other dividers for AGP and PCI buses, although for some reason most mainboards do not support this feature.

This way, the higher is the processor bus frequency in the BIOS Setup, the higher rise the processor clock frequency, the memory frequency, HyperTransport frequency and even AGP/PCI frequency if we are talking about VIA K8T800. That is why in order to avoid any possible problems during overclocking, when the speed will be limited not by the CPU, but by AGP/PCI devices or the chipset, it makes much more sense to overclock Athlon 64 by increasing its clock frequency multiplier. However, unfortunately, you will not be able to do it with the today’s Athlon 64 3200+ processors. Although their multiplier is unlocked, it can be set to 10x maximum, which means that there is no room to increase it any further: the nominal clock multiplier of the today’s Athlon 64 3200+ processors is the maximum multiplier possible at all. So, the only way to overclock these processors remains the bus frequency. In this case it is very helpful that you can apply special lowering coefficients to the frequencies of other buses, which depend on the processor bus frequency. As for the memory and HyperTransport frequencies, there are no problems here. AGP/PCI frequency on nForce3 150 based mainboards is set independently, and on VIA K8T800 based mainboards the growth of the processor bus may cause some issues with the AGP/PCI devices.

 
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