Does the CPU throttling issues (e.g. clock speed stuck at 800MHz) on the W520 still exists with newest BIOS update?
The CPU throttling issues have been resolved a few BIOS revisions ago. (BIOS 1.33 and newer). However, if CPU and Nvidia Quadro GPU are both utilized on battery with High Performance power plan, the CPU may be throttled to 1.5GHz as the battery is unable to supply enough power (wattage). Individual results may vary based on version of CPU i5 / i7 and max rated clock speed.
Real world application use vs synthentic benchmark results may vary. If multiple cores of the CPU are engaged, lower top Ghz clock speeds may be indicated - this is normal operation of the turboboost feature operating within the total power envelope of the system.
To achieve maxium system performance when simulataneously drawing upon CPU and GPU, connect the system to AC and ensure the battery is installed.