Merom against Yonah: Overclocking Duel

by Aleksey Razin

[ 05/05/2006 | 03:12 PM ]

The well-known overclocker and hardware enthusiast aka Coolaler has already tested a mobile Yonah processor in the i975X based mainboard having enabled the SLI support in the modified driver. Of course, we expected more exciting experiments from the guy.

Coolaler managed to successfully overclock future Core Duo T7400 (2.16GHz) on the 0.065micron Merom core and described his results in three on-line sources: his own site, XtremeSystems.org and in a review posted on IAMEXTREME site.

He managed to get hold of a Merom engineering sample: model T7400 (2.16GHz) with 4MB of shared L2 cache and 667MHz bus support. This CPU is based on A1 core stepping and the mass production processors are most likely to be B0 core stepping based. Therefore, we would like to prevent you from making any hasty conclusions.

With the help of a highly efficient Tuniq Tower 120 cooler he managed to overclock his CPU to 2.92GHz by raising the Vcore from 1.2V to 1.4V. The processor was compared against Yonah T2600 (2.16GHz), which is not only its architectural predecessor but also works on the same nominal clock speed. He overclocked Yonah up to 250MHz on the bus, while Merom could only reach 225MHz on the bus. Coolaler believes it is the peculiarity of the Merom and Conroe processors: they do not favor high bus frequencies. Although it could also be the limitations imposed on this particular sample or the entire A1 stepping batch.

Note that the maximum clock frequency multiplier of Merom T7400 processor equals 13x, which could help overclock this CPU quite efficiently if it hadn’t been for the notorious limitation of the bus overclocking. In idle mode the EIST technology drops the CPU frequency to 1.0GHz (6x166MHz) and only if we raise the bus frequency to 200MHz the total idle speed reaches 1.2GHz (see the screenshot above).

According to the benchmark results we can say that Merom is faster than Yonah working at the same clock speed. Namely, Merom need to reach 2.8GHz clock speed to show the same performance results as the Yonah processor working at 3.0-3.2GHz.

I would like to draw your attention to the fact that first-generation Merom processors supporting 667MHz bus will be compatible with mainboards and chipsets designed to support Yonah. For example, the desktop AOpen i975X a-YDG needed just a BIOS update to start working with Merom.

Looks like Conroe will not really affect the popularity of the “Mobile-On-Desktop” platform as we would have expected it to: some hardware enthusiasts will love overclocking their Merom processors in desktop mainboards.