Prescott effects on motherboard power circuits

Motherboards/Intel S775 by KeithSuppe @ 2004-05-10

The Prescott had finally arrived, and knowing the risks I would be taking even after learning of the chip?s defeatist architecture, I went ahead and purchased the world?s first CPU built upon a 90nm process, and compatible (at least initially) with Socket-478. I?m no martyr, however; I?ve done this for you the reader. Knowing Anandtech had tested Prescott up against Northwood, and Northwood bested the 90nm chip in most benchmarks at default speeds, was ancillary to why. This question had to be answered, and furthermore was Prescott salvageable?

  • prev
  • next

Page 2

Given the architectural dialogue between chipmaker and motherboard maker, one must presume both manufacturers had an idea such problems could develop. Why then didn't they make the appropriate modifications to their Socket-478 "Prescott Ready" platforms? I believe the answer is simple. Knowing the release of a socket LGA775 Prescott was just around the corner, manufacturers chose to eschew any circuit changes on their Socket-478 platforms, even though they are purportedly Prescott compatible. The very small number of Enthusiast's who might push Prescott to such "extremes" simply didn't justify the cost of replacement parts, and redesigning of the circuits in question.

Problem is, the excessive temps seen above were not the result of overclocking in the first screenshot, but simply running Seti@Home. And 3D intensive applications stressed the board so much rebooting was common, anytime ambient temps weren't ideal. As the screenshot's above empirically verify, these problems are bound to persist, and what's more troubling is the lack of sensors on motherboards able to monitor such temps. The Abit AI7 is the only Socket-478 90nm compatible motherboard I know of, which specifically monitor's the PWM circuitry. Had it not been for uGuru's being equipped with this unique temp sensor, I'm sure this would have alluded me.


Now to determine the precise cause for these PWM temperature extremes, in the follow-up to [H]ardOCP's Prescott 2.8E piece, Prescott Tweaks Dangerous, Kyle reprints the following statements from MSI concerning the elimination of Vcore adjustment from it's 865PE Neo2 motherboard BIOS, and why;


Madshrimps (c)



How many Enthusiasts know about Dynamic VID? I've found some very useful info at Iamnotageek.com in an article by Martin entitled Prescott Info. In reading further through Intel's White Paper titled; VRD (Voltage Regulator Down) the 478-Socket platform is designed to regulate voltage in order to keep the Processor cool during clock-cycle intensive periods. Section 2.4 of the VRD paper states;


Madshrimps (c)



These features while excellent safeguards for average use, certainly present problems for Overclocker's raising Vcore. But what about circumstances where the Processor may be pushed beyond average workloads, but not necessarily overclocked such as my first screenshot exemplifying PWM temps at default speed/Vcore? Whenever Prescott is under heavy workloads, this exacerbates Socket-478 Thermal Clock Throttling "like" features. However due to the Processor's high current requirements, which are exponentially aggravated by the failure of motherboard makers to beef up the PWM circuitry, there seems to be a feedback which is becomes detrimental to the motherboard's power circuitry. The following quote was taken from the conclusion notes in section 2.8.1 from the VRD paper;


Madshrimps (c)
  • prev
  • next