EPoX EP-8KTA3 Socket-A KT133A ATX

Overclocking: What is the limit this time?

It’s clear that the KT7A-RAID is designed for hardware enthusiasts, just like other ABIT motherboards, and it would definitely be useful to see how much overclocking this board can handle.  From our coverage on the KT133 motherboard roundup, we have seen the advantage of overclocking by increasing the multiplier ratio setting.  The same case still carries on to the KT133A chipset.

On the other hand, focusing on FSB overclocking is worth a closer look with the new official support for 133MHz FSB operation.  We have all seen the poor FSB overclocking by the KT133 chipset, where speeds of higher than 110 - 115MHz are basically unachievable.  Now with the KT133A chipset, we are sure that FSB speeds of up to 133MHz are no longer a problem, but it would be interesting to find out how high above 133MHz can we get the FSB speed to.

In order to find out about that, we took a 1GHz Athlon processor, a Mushkin PC133 CAS2 PC133 SDRAM, and a NVIDIA GeForce2 GTS as our test bed.  We started the testing by setting the 1GHz CPU to run at 133MHz FSB, thus having a  multiplier ratio of 7.5.  Then we gradually increased the FSB speed and ran tests to make sure the system is stable at that speed.  If needed, we also tried to set the CAS latency to 3 and all other memory timings to as slow as possible, so that the PC133 SDRAM would not be the limiting factor.  Moreover, when the FSB got to a certain point, we lowered the multiplier ratio setting so that the clock speed of the CPU remained close to 1GHz.

For our testing, initially with CAS2 and normal memory settings, the highest FSB speed we achieved was 140MHz.  At that speed we could still run SYSMark 2000, Quake III Arena, and Content Creation Winstone 2000 with no problem.  However, with the FSB speed set to 145MHz, the system couldn’t even boot into Windows correctly.

We then lowered the CAS setting to 3 and reduced any other memory related category in the BIOS, allowing us to get the FSB up to 145MHz and ran all the tests with no problem.  At 150MHz, which is the next FSB speed setting, the system would not even boot.

From the KT7A-RAID review, the highest FSB we could get for fast memory setting was 144Hz, and for slow memory setting, we went as high as 147MHz.  We can see here that the EP-8KTA3 is being edged by several megahertz.  This is mainly due to the lack of 1MHz increments support for FSB speeds.  As we notice, for FSB speeds above 140MHz, where we have proved that they are highly achievable, the EP-8KTA3 supports 140 / 145 / 150 / 155 / 160 / 166MHz.  These 5MHz jumps, in general, can be very severe hit for extreme overclocking. 

Furthermore, the AGP voltage tweaking can be useful in overclocking.  For some reasons, when we go from 140MHz to 145MHz FSB, when entering Windows, the video signals were corrupted, and our NVIDIA GeForce2 GTS video card was not detected correctly.  Raising the voltage by 0.2V resolved the issue easily.  However, even raising the voltage by 0.5V doesn’t help in further overclocking.