From the very beginning NetBurst microprocessors have had a unique feature called thermal throttling that is supposed to keep the chip from burning out when cooling is not proper by “skipping” cycles or shutting down the computer. While all 0.18 micron Pentium 4 and Xeon chips as well as 0.13 micron Pentium 4 and Xeon processors have clearly determined levels when the CPU starts to “miss” cycles, this is not effective for the 90nm chips, which are reportedly marked according to individual peculiarities.

Each individual Intel Pentium 4 or Xeon processor at 90nm process technology will have an individually tested and set #PROCHOT level – the level of temperature when CPU starts to “throttle”, based upon the leakage characteristics of the CPU, Real World Technologies and some other sources report.

Power leakage is current flowing in a circuitry that is not being used at the moment. While the problem has been around for decades, it became dramatically serious with Intel’s Pentium 4 E processors known as Prescott.

Apparently, there may be significantly various leakage power characteristics for Intel’s 90nm chips, as a result, different CPUs have different heat dissipation and temperature peculiarities. This is the reason why is it necessary to test all chips individually to set the #PROCHOT level for a particular chip, not a batch of chips as previously. Another reason of the move may be an assumption that Intel’s future chips may also run into even more serious power leakage issues.

It remains to be seen how individual testing of every chip results on the manufacturer’s ability to deliver the 90nm CPUs in quantities on timely basis as well as gross margins for such products.

Representatives for Intel did not comment on the report at press time.