Following extensive performance testing under numerous workloads,
we’ve identified that there is a missing digital key in the
firmware that impacts the thermal management system and could
drive clock speeds down under heavy thermal loads on the new
MacBook Pro. A bug fix is included in today’s macOS High Sierra
10.13.6 Supplemental Update and is recommended. We apologize to
any customer who has experienced less than optimal performance on
their new systems. Customers can expect the new 15-inch MacBook
Pro to be up to 70% faster, and the 13-inch MacBook Pro with Touch
Bar to be up to 2X faster, as shown in the performance results on
I figured it was a bug when some tests were showing that performance improved on the Core i9 15-inch MacBook Pro after disabling two of the six cores. Apple told me that this thermal bug affects all new MacBook Pros — not just the Core i9 model — and older models are not affected. Anyone with a new MacBook Pro should now see the fix via Software Update.
I’d love to hear a further explanation of exactly what this “missing digital key” is. I think it’s just the sequence of bytes that configure the thermal settings for the CPU.