PTAB

IPR2018-01312

InTel Corp v. VLSI Technology LLC

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1. Case Identification

2. Patent Overview

  • Title: Power Management for Cache Memory
  • Brief Description: The ’014 patent relates to a method and device for managing power consumption in electronic components, particularly cache memory. The core concept involves determining whether to power down a portion of a component by evaluating a relationship between an estimated power gain from the shutdown and an estimated power loss that would result.

3. Grounds for Unpatentability

Ground 1: Claims 12-14, 18, and 20 are obvious over Takahashi

  • Prior Art Relied Upon: Takahashi (Patent 5,761,715)
  • Core Argument for this Ground:
    • Prior Art Mapping: Petitioner argued that Takahashi alone rendered all challenged claims obvious. Takahashi disclosed an information processing device with power reduction capabilities that selectively powered down portions of a cache (cache ways) to reduce power consumption. The decision to power down was made by comparing a measured "cache-miss rate" against a "predetermined value threshold." Petitioner contended this was a direct proxy for the ’014 patent's claimed determination "in response to a relationship between an estimated power gain and an estimated power loss." Specifically, the cache-miss rate served as the proxy for estimated power loss (since misses increase dynamic power), and the predetermined threshold served as the proxy for estimated power gain (the benefit of powering down). Takahashi's cache-miss rate measuring circuit was also argued to teach the limitations of generating "cache statistics" (claim 18) and monitoring "integrated circuit behavior" (claim 20).
    • Key Aspects: The core of this argument was that the ’014 patent merely recited the same fundamental trade-off that Takahashi already addressed and solved using well-understood proxy metrics, making the claimed invention an uninventive description of the prior art's function.

Ground 2: Claims 12-14, 18, and 20 are obvious over Takahashi in view of Hu

  • Prior Art Relied Upon: Takahashi (Patent 5,761,715) and Hu ("Let Caches Decay: Reducing Leakage Energy via Exploitation of Cache Generational Behavior," May 2002).

  • Core Argument for this Ground:

    • Prior Art Mapping: This ground asserted that even if Takahashi alone was insufficient, the combination with Hu rendered the claims obvious. Takahashi provided the foundational system for dynamically powering down cache ways based on operational metrics. Hu was argued to explicitly teach the missing element alleged by the patentee during prosecution: an explicit comparison of power gain versus power loss. Hu described a method to "measure the static power saved by turning off portions of the cache, and then compare it to the extra dynamic power dissipated" from the resulting cache misses. The combination of Takahashi’s system with Hu's explicit power gain/loss calculation allegedly taught every limitation of independent claim 12.
    • Motivation to Combine: A Person of Ordinary Skill in the Art (POSITA) would combine the teachings because both references addressed the identical problem of reducing power consumption in a CPU cache using similar techniques. A POSITA would have been motivated to replace or supplement Takahashi’s proxy-based determination (cache-miss rate vs. threshold) with Hu's more explicit and refined method of calculating and comparing actual power gain and loss values. This would have been a predictable and desirable modification to improve the efficiency and reliability of Takahashi’s power-saving system.
    • Expectation of Success: A POSITA would have had a high expectation of success in combining the references. Applying Hu's known technique for analyzing the power trade-off to Takahashi's device was presented as a routine modification that would predictably improve the existing system, not an inventive step requiring undue experimentation.

  • Additional Grounds: Petitioner asserted that claim 20 was also obvious over Takahashi in view of Gunther (Patent 5,781,783), and over the combination of Takahashi, Hu, and Gunther. These grounds used Gunther to provide more detailed teachings on monitoring integrated circuit behavior (e.g., L1 cache hits/misses) to predict future activity and trigger power-down states, strengthening the obviousness rationale for claim 20's monitoring limitations.

4. Key Technical Contentions (Beyond Claim Construction)

  • A central contention was that the prior art’s use of proxy values for power analysis was equivalent to the claimed invention. Petitioner argued that a POSITA would understand that Takahashi's "cache-miss rate" is a direct proxy for "estimated power loss" and its "predetermined threshold" is a proxy for "estimated power gain." The petition asserted that the ’014 patent merely re-labeled these known concepts from the prior art without introducing any inventive technological improvement.

5. Relief Requested

  • Petitioner requests institution of an IPR and cancellation of claims 12-14, 18, and 20 of Patent 8,020,014 as unpatentable.