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LOSTCIRCUITS
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| Intel Pentium4 840 Extreme Edition and 840D .... the name of the rose ... | |
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(Review by MS June 20, 2005) |
| AMD Athlon 64 3800+ (Venice) |
Power to the Cores!
Last not least, before going into the main part of this article, there is the issue of power. Power concerns have been amongst the big issues plaguing the Prescott core and since the dual core architecture is a derivative of the Prescott, the issues might duplicate. Intel specifies the ICCmax for the ‘840 EE as 125A, which at 1.45V result in whopping 181 W processor power consumption. In reality, the situation is not that bad since there is a somewhat linear, load dependent voltage droop of up to 0.13V (at ICCmax). Therefore the maximum power is only 125A * 1.32V or 165 W. Keep in mind that this is the worst case scenario and that in real life, there are no applications that could result in that much power consumption. Realistically, we can expect to not exceed 80-85% of this theoretical value.
Time to take a look a bit more in detail at the architecture of Intel’s Pentium4 840 ExtremeEdition. Keep in mind that the ‘840 ExtremeEdition is not the only dual core Intel CPU currently on the market, there is also the Pentium4 D which is different from the P4 840 ExtremeEdition in that it does not support HyperThreading.
Technical Specs
Smithfield die shot: The two cores are sitting side by side. One thing worth mentioning is that, in contrast to e.g. the AMD Athlon64-X2 core, the two cores are not mirror-symmetric twins but show the same orientation.
The ExtremeEdition is recognized as four logical cores. The 840D, which does not support HT only shows as two cores. Since technically we were using the ExtremeEdition with HT turned off in the BIOS, we refer to it as "P4 840 EE-" in some cases throughout the review, which is synonymous to the "840D".
Aside from the obvious, two of the above mentioned specs are particularly noteworthy, that is, the two cores are based on the original “Prescott1” design with the 1MB L2 cache and furthermore, the entire CPU is running at an 800 MHz processor side bus. Given the fact that there is relatively little performance associated with the 2MB L2 of the “Prescott2” and moreover, larger caches are somewhat more difficult to manage, the 1MB L2 cache design is not overly surprising, not to mention the additional power consumption by the high-speed SRAMs.
On the other hand, given the established performance benefit of the 1066 MHz bus, it is, at least at first glance, a bit surprising to see the 800 MHz bus interface. Keep in mind, though, that, as we reported first, in the megahertz madness no provisions were taken to support anything lower than a 14x multiplier on the Prescott core. This omission is now coming back to bite Intel since the lowest clock speed achievable with a 1066 MHz bus would be 3.73 GHz, which would push the power consumption into the 230-250 W bracket. As a result, the only way at the current state of technology to even stay within a reasonable power specification is to stick with the, albeit slower, 800 MHz PSB.
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Pentium 4 840D (dual core) |
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